1

F . Structural Light Alloy Materials

Organizers: Baiqing Xiong, Xujun Mi, Kechao Zhou, Fusheng Pan, Xu Huang, Yongqing Zhao, J. C.

Huang, Hiromi Nagaumi, Yong-Tai Lee, Linzhong Zhuang

F-01

Precipitation Hardening and Intergranular Corrosion Resistance of Zn Modified 5××× Series Al Alloy

Shengli Hou1, Di Zhang1, Jishan Zhang1, Linzhong Zhuang1,2

1. State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing,

Beijing 100083, People’s Republic of China.

2. TaTa Steel, 1970 CA IJmuiden, The Netherlands

In this presentation, we systematically investigate the precipitation hardening behavior and intergranular corrosion

resistance of Zn modified 5××× series Al alloy during artificial aging treatment. The effects of single step

aging, pre-aging and natural aging on the precipitation hardening behavior and intergranular corrosion resistance

are detailed. The designed alloy achieves higher strength, elongation and improved intergranular corrosion

resistance, when the alloy is heat treated at 90℃ for 24h and subsequently aged at 140℃ for 10 to 15h. The

formation of relatively stable GP zone of T phase during pre-aging rather than natural aging results in higher

mechanical strength during subsequent artificial aging at relatively high temperatures. The intergranular corrosion

susceptibility of Zn modified alloy is clearly affected by the continuous distribution of grain boundary precipitates

and the formation of precipitate free zone adjacent to the grain boundary.

F-02

Surface Characterization Techniques in Advance Material Development

Fu Chao

Wintech Nano-Technology Services Pte.Ltd

Solid material surface and material interface are the key area for semiconductor material application development.

We define the surface as in material top surface down to 100nm. There are various type of technique to

characterize the material property within this range. This paper will be emphasizing on various techniques

comparison between AFM, SEM, TEM, TOF-SIMS, XPS, Auger, FTIR.

F-03

Properties and microstructure of wheel prepared by liquid die forging of new type Al-Cu alloy

Hong Xu

North University of China

The new Al-Cu aluminum alloy wheel was prepared by the liquid forging technology and conducted by the heat

treatment, and the partition method, metallography, mechanical properties, composition distribution and fracture

observation method were used to study the liquid forging forming rules of new Al Cu aluminum alloy. The results

showed that: there was serious Cu segregation of the wheel specimen checked by the fluorescence spectrometer.

The best heat treatment system for the new Al Cu aluminum alloy prepared by the forging forming was 530±5℃

/4h + 535±5℃/24h, and the water quenching system was 155±5℃/4h. The fracture morphologies heated by T6

and T5-1 were flat, tough nest, poor plastic. The fracture morphologies heated by T4 had the complete resiliences,

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but there was no the residual metallography. The sample treated by T4 had the best extension rate during the three

heat treatment systems. The sample treated by T5-2 had many tough nests in the fracture morphologies, but the

tough nests existed residual partially broken alloy phases. The fracture morphologies heated by T5-3 had many

tough nests, but no residual partially broken alloy phases existed in the tough nests. The fracture mechanism of

specimens was the intergranular fracture.

Al-Cu alloy; liquid die forging; tensile property; microstructure

F-04

Effect of EMS above Liquidus Temperature on Structure Re-finement of

Al-11%Zn-3%Mg-1%Cu-0.13%Zr Alloy

Tianyang Guan, Zhifeng Zhang, Yuelong Bai, Min He

General Research Institute for Nonferrous Metals

Al-Zn-Mg-Cu alloy with high strength and high stiffness is increasingly being applied in the aerospace industry.

Because there exist high alloy content and a wide range of crystallization temperature for such alloy,

inhomogeneous structure and composition segregation cannot be avoided during casting process. Electromagnetic

stirring (EMS), as an advanced melt treatment technology for the purpose of homogeneity of melt temperature and

composition, plays an important role in the grain refinement. However, much work was mainly focused on the

effect of EMS on the grain refinement in the solid-liquid state.In this study, an Al-11%Zn-3%Mg-1%Cu-0.13% Zr

alloy was used to investigate the effect of EMS at various temperatures above liquidus on structure refinement.

The results indicated that the grain size was reduced greatly and the more homogeneous structure was achieved,

and the refinement mechanism was perhaps attributed to an instantaneous nucleation of numerous Al3Zr in the

superheating melt under EMS.

Al-Zn-Mg-Cu alloy; electromagnetic stirring; liquidus temperature, nucleation; grain refinement

F-05

Properties changes and fracture behavior of Cu-Ni-Si/Al-Mg-Si clad composite wire after heat treatment

Zhen Yang, Xujun Mi, Haofeng Xie, Lijun Peng

State Key Laboratory of Nonferrous Metals & Processes, General Research Institute for Nonferrous Metals

The copper-clad aluminum (CCA) composite wire has been widely used in cable industry. Especially in the

development of aerospace, the light weight character of wire is particularly important. To improve the mechanical

properties, Cu-Ni-Si alloy and Al-Mg-Si alloy are employed to replace pure copper and pure aluminum

respectively. The objective of this work is to find the appropriate heat treatment conditions, which produce

optimal combination properties of Cu-Ni-Si/Al-Mg-Si clad composite wire. The wire was fabricated by a drawing

process and heat treated with different temperatures and time. Mechanical and electrical properties, which are

determined by outer Cu-Ni-Si, internal Al-Mg-Si and interface properties, were measured and analyzed. The

tensile fracture of Cu-Ni-Si/Al-Mg-Si clad composite wire was investigated by scanning electron microscope.

Below 300℃, the fracture shows that Cu-Ni-Si and Al-Mg-Si combines well, the intermetallic compounds play a

role as a bridge to connect two alloys. However, above 350℃, the brittle intermetallic compounds separate and

crack, with the growing gap of elongation between Cu-Ni-Si and Al-Mg-Si.

fracture; clad composite wire; intermetallic compounds; properties; interface

F-06

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Effect of solution treatment on microstructure and mechanical properties of 7A56 aluminum alloy

Fengbin Guo1, Baohong Zhu1, Longbing Jin1, Guojun Wang2, Hongwei Yan1, Xiwu Li1, Zhihui Li1, Yongan

Zhang1, Baiqing Xiong1

1. State Key Laboratory of Nonferrous Metals and Processes, General Research Institute for Nonferrous Metals

2. Northeast Light Alloy Co., Ltd.

The effects of solution temperature and time on the microstructure and mechanical properties of a novel 7A56

aluminum alloy plate were investigated by OM, SEM, DSC, conductivity and hardness test. The results indicated

that the coarse second phases in the as-rolled plate mainly contained AlZnMgCu quaternary phases and Al7Cu2Fe

phases, without Al2CuMg phases. The number of the second phases gradually reduced with the increase of

temperature(450-480°C) and time(1-8h) during the solution treatment, and the soluble second-phase particles

has been completely dissolved into the matrix under 470°C for 4h, while residual phases were mainly Fe-rich

phases along the grain boundaries. When the temperature was above 480°C, overburning took place. The

mechanical properties treated at 470°C for various time were tested. After solution treated at 470°C for 4h, the

quenched conductivity and peak-aged hardness of the alloy were 30.8 %IACS and 204 HV respectively.

7A56 aluminum alloy; solution treatment; microstructure; properties

F-07

Promoted inoculation effects of Al-10Si-2Fe master alloy on primary silicon in Al-20Si alloy assisted with

TiB2

Wenhui Yu, Yong Zhang, Aolei Jiang, Tingliang Yan, Hongliang Zheng, Xuelei Tian

Shandong University

Cluster-assisted crystallization was further investigated in Al-Si melts with the inoculant Al-10Si-2Fe master alloy

assisted with Al-5Ti-B master alloy by optical microscopy (OM), thermal analyses and scanning electron

microscopy (SEM). TiB2 is reconfirmed to increase the solution of phosphide AlP in the melts and to promote Si

nucleation as the coupling particles of TiB2·AlP act as nucleating substrates. The results show that the inoculation

effect of Al-10Si-2Fe alloy cannot be promoted with the assistance of Al-5Ti-B master alloy in high purity alloys

due to the absence of potent nucleating substrates. However, primary Si is further refined after being inoculated

with Al-10Si-2Fe and Al-5Ti-B master alloys simultaneously in commercial purity alloys compared with that

inoculated with the master alloys separately. Meanwhile, the cooling curves confirms the assisted effects of

Al-5Ti-B alloy. Swells on silicon provide the evidence of attachment of pre-nucleation clusters during Si

crystallization. It is deduced that the pre-nucleation clusters can reinforce the nucleating ability of potential

heterogeneous nucleating substrates.

Primary silicon; Al-Si alloy; assisted nucleation; Pre-nucleation clusters

F-08

Effect of copper content on quench sensitivity in novel Al-Zn-Mg-Cu alloys containing high zinc content

Jinsheng Chen, Xiwu Li, Baiqing Xiong, Yongan Zhang, Zhihui Li, Hongwei Yan, Hongwei Liu, Shuhui Huang,

Lizhen Yan

State Key Laboratory of Nonferrous Metals and Processes, General Research Institute for Nonferrous Metals,

Beijing 100088, China

The effect of copper content on quench sensitivity in novel Al-Zn-Mg-Cu alloys containing high zinc content was

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investigated. Methods: Three alloys with different copper content were tested by Jominy end quench test,

including electrical conductivity and hardness measurement, temperature collecting, and transmission electron

microscopy (TEM).Results: The results indicate that the alloy with the highest copper content shows the largest

changes as the average cooling rate varying from 29.2 to 1.5 ℃•s-1, which electrical conductivity increases from

16.5 to 18.2 MS•m-1 and hardness decreases from HV 211.7 to HV 176.0. Moreover, the amount and size of

quenched-induced precipitates in this alloy are larger than the other two alloys with lower copper content at the

same distance from quenched end. Conclusion: Higher copper content leads to higher quench sensitivity in novel

Al-Zn-Mg-Cu alloys with the same content of magnesium and zinc.

Al-Zn-Mg-Cu alloy; Copper content; Quench sensitivity; Jominy end quench test; Precipitate

F-09

The effect of fatigue pre-deformation on the mechanical behavior of Al-4.0 wt.% Cu alloy

Qing-Shuang Song1, Dong Han1, Ying Yan1, Xiao-Wu Li1,2

1. Department of Materials Physics and Chemistry, School of Materials Science and Engineering, Northeastern

University, Shenyang 110819, P.R. China

2. Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University,

Shenyang 110819, P.R. China

A variety of engineering structural components are usually subjected to alternating loads under service conditions,

leading to the change (mostly degradation) of their mechanical properties; this will seriously affect the service

safety of components. Many studies have thus been focused on the cyclic pre-deformation effect on the

mechanical behavior of materials in recent years. However, studies are still rarely focused on the effect of fatigue

pre-deformation on the mechanical behavior of solution- and aging-treated alloys. Therefore, in the present work,

an Al-4.0 wt.% Cu alloy was selected as the target material, and it was first solution-treated or

solution+aging-treated, and then cyclically pre-deformed to different pre-fatigue levels D (= Ni / Nf, where Ni and

Nf are the applied cycles and fatigue life, respectively). The pre-fatigued alloy specimens were then subjected to

tensile tests up to failure. The corresponding damage features and deformation microstructures were also observed.

The aim is to provide reference date for enriching the micro-mechanisms for the fatigue pre-deformation effect on

the mechanical behavior of materials.

The results show that, with the prolonging of aging time, ultimate tensile strength sUTS and yield strength sYS

increase, and uniform elongation d decreases. After the solution-treated alloys are pre-fatigued to different D and

then loaded to tensile rupture, in comparison to the as-solution-treated state, the sYS obviously increases and does

not obviously vary with increasing D, whereas the sUTS at different D basically comparable to that in the

as-solution-treated state, and the d slightly decreases. After the aging-treated alloys are pre-fatigued to different D

and then loaded to tensile rupture, the notable increase in sYS takes place as compared to the as-aging-treated

state, but it almost does not change with the raising of D. The d at different D basically does not change and it is

nearly close to that in the as-aging-treated state, whereas the sUTS is basically comparable to that in the

as-aging-treated state at D ≤ 20%, and then starts to decrease at D > 20%.

During an aging treatment at 160 oC, with the prolonging of time, the type of precipitates transfers from the flaky

GP zone into the disc-shaped θ’, and then into the coexistence of disc-shaped θ’ and a small amount of

granular θ; the content of precipitates increases. After the solution-treated alloy is loaded to tensile failure, the

dislocation structure were observed in the form of networks, whereas for the aging-treated alloy, with the

prolonging of aging time, the dislocation density increases after tension, and the tangled dislocations as well as the

obvious interactions between dislocations and precipitates were observed. The cyclic pre-deformation on the

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solution-treated alloy promotes the precipitation of fine θ particles and the formation of separated dislocation

lines, thus resulting in the increase in sYS. For the solution-treated and then pre-deformed alloys, with increasing

D, fine θ particles and the dislocation density increase after tension, and the dislocation structures change from

the tangled and cellular arrangements into the dominated network form. In contrast, as the alloys

solution+aging-treated at 160oC for 16h were pre-deformed to D = 5 ~ 75% and subsequently loaded to tensile

rupture, the higher-density dislocations exist in the form of tangles, and the interactions between dislocations and

precipitates are stronger at D ≤ 20%; however, at D > 20%, the dislocation density starts to decrease, and the

interactions between precipitates and dislocations become weakened, thus leading to the decrease in sUTS.

The cracks are mainly formed at grain boundaries (GBs) after tensile deformation , but a lot of kinks insides

grains and the obvious GB extrusion are observed in the solution treated and then pre-deformed alloy.

In a word, a cyclic pre-deformation at D = 5 ~ 75% improves the sYS of solution-treated and aging-treated Al-4.0

wt.% Cu alloys, simultaneously without the loss in sUTS at D ≤ 20% and d at different D for the aging-treated

alloy, whereas for the solution-treated alloy, there is only a slight decrease in d and sUTS at different D.

Al-4.0wt.%Cu, solution treatment, aging treatment, fatigue pre-deformation, tensile propert, microstructure

F-10

Investigation on the microstructure evolution of Al-matrix in homogenized 7A56 aluminum alloy

Da Xu1, Zhihui Li1, Guojun Wang2, Longbing Jin2, Hongwei Yan1, Xiwu Li1, Yong'an Zhang1, Baiqing Xiong1

1. General Research Institute for Nonferrous Metals Beijing

2. Northeast light alloy Co., Ltd.

Microstructure evolution of Al-matrix in homogenized 7A56 alloy was investigated by SEM, XRD, DSC,

electrical conductivity and hardness measurement. After 380℃/24h, 430℃/24h and 470℃/24h treatment, the

relative content of AlZnMgCu phase decreases to 97.8%, 49.2% and 8.7%, respectively, compared to as-cast 7A56

alloy. Correspondingly, the enthalpy in DSC curves of the melting of AlZnMgCu phase decreases to 17.24J/g,

10.20J/g and 0.18J/g, respectively , while the value of as-cast alloy is 17.16J/g，indicating that AlZnMgCu phase

hardly dissolved at 380℃. With the temperature increasing, the hardness increases while the conductivity

decreases. The evolution can be due to the dissolution of the solute atoms into Al-matrix, leading to a heavier

lattice distortion that the lattice constant increases to 4.0536.

7A56 aluminum alloy; homogenization; Al-matrix; lattice distortion

F-11

Fabrication of Hybrid Al Sheets with Improved Mechanical and Corrosion Properties by Roll-Bonding

Process

Cha Yong LIM1, Seong Hee LEE2

1. Korea Institute of Materials Science

2. Mokpo National University

Hybid Al sheets were fabricated by multi-layer accumulative roll-bonding process. Several Al sheets (AA1050,

AA5052, AA6061) with 1 mm thickness, 30 mm width and 300 mm length, were first degreased and wire-brushed

for sound roll bonding. The different sheets were then stacked on top of each other and rolled by 50% reduction

rate without lubrication at room temperature. The bonded sheet was cut into two pieces of the same dimensions

and the same procedure was repeated up to 6 cycles. Microstructural evolution of bonded sheets with the number

of the ARB cycles was investigated by optical microscopy (OM), transmission electron microscopy (TEM), and

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electron back scatter diffraction (EBSD). The grain size decreased gradually with the number of ARB cycles. The

strength of the bonded sheets increased with the number of ARB cycles. The improved strength and elongation

were obtained by applying annealing treatment.

Hybrid Al, High strength, High elongation, Roll bonding

F-12

Morphological Studies on Fe-rich Phase in Die-cast Al Alloy with Trace Additions of Mn and Cr

Zhiqiang Qiu1, Xiaoshu Zeng1, Xi-Xin Rao1, Yan Ding2, Lan Luo2, Yong Liu1

1. Key Laboratory of Near Net Forming of Jiangxi Province, Nanchang University, Nanchang 330031, People’s

Republic of China

2. School of Materials Science and Engineering, Nanchang University, Nanchang 330031, People’s Republic of

China

The evolution of Fe-rich phase in a die-cast AlSi9Cu3(Fe) alloy has been investigated over two levels (0.6,

1.3wt.%) of iron (Fe), and one level (0.1wt.%) of manganese (Mn) and chromium (Cr). Metallographic and image

analysis techniques have been used in order to quantitatively evaluate the morphological and dimensional

variations of Fe-rich phase with different contents of Fe, Mn and Cr. The results indicate that the Chinese scrip

Fe-rich phase appears in the alloy with 0.6wt.% Fe combined with trace Mn, while the blocky shape of Fe-rich

phase appears combined with trace Cr. Under the coexistence of trace Mn and Cr, a large number of Chinese

script Fe-rich phase could be visible in the low iron-bearing Al alloy(0.60 wt.% Fe). At high Fe levels (1.30 wt.%),

large Fe-rich phases with polyhedral morphologies are observed with the trace addition of Cr, while fish-bone and

polyhedral morphologies Fe-rich phase could be simultaneously observed with the addition of both Mn and Cr.

The results reveal that trace Mn promotes the formation of Fe-rich phase with Chinese scrip morphologies, while

trace Cr benefits the formation of blocky or polyhedral morphologies Fe-rich phase. The combination of Mn and

Cr could promotes the formation of Chinese scrip, fish-bone or polyhedral morphologies Fe-rich phase. The

mechanism of morphology evolution of Fe-rich phase has been discussed by using of the sludge factor and

crystalline orientation growth with and without trace Mn and Cr.

Al alloy, Fe-rich phase, Sludge factor,Trace alloying

F-13

Optimization of CSP process parameters for quality improvement of ADC12 alloy billets using regression

analysis

Ye Wang1, Hongyu Xu1, Lianjie Niu2, Zesheng Ji1, Duo Dong3, Dongdong Zhu3

1. School of Materials Science and Engineering, Harbin University of Science and Technology, 150001, China

2. Department of Mathematics and sciences, Hebei Institute of Architecture and Civil Engineering, 075000, China

3. College of Mechanical engineering, Quzhou University, 324000, China

In order to improve destiny of the billets of ADC12 alloy prepared by Chips Solid Pressing (CSP) process, the

design of experiment technique, range analysis and the regression analysis are introduced to optimize the process

parameters of CSP process in this paper. The effect of pressing temperature, pressing pressure and packing time on

the destiny of ADC12 alloy billets is investigated by using the orthogonal array and multiple nonlinear regression

analysis to characterize the trend of destiny changes. The effectiveness of selected pressing parameters for destiny

of ADC12 alloy billets is verified through analysis of variance (ANOVA) and confirmed experiment. The results

indicate that the optimized process parameters, including a pressing temperature of 250oC, pressing pressure of

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640MPa and packing time of 45 seconds, can be used to obtain the most compact billets of ADC12 alloy prepared

by CSP process in ZL205A castings.

optimization; chips; ADC12; CSP process; multiple nonlinear regression analysis

F-14

Effect of enhanced solution treatment on microstructure and mechanical properties of AlCuLiScAg alloy

Ruibin Yang, Feizhou Wang, Yunjie Zhang, Zhongxia Liu, Jiefang Wang

Key Laboratory of Materials Physics (Zhengzhou University), Ministry of Education, Zhengzhou, China

Objective: To develop the enhanced solution treatment to improve the mechanical properties of AlCuLiScAg

alloy.

Method: The reference solution treatment process (heating samples to 520 oC and holding for 2h) and two kinds

of enhanced solution treatment processes (first heating the samples to 520 oC and holding for 2h, then heating the

samples to 540 oC with heating rates of 60 oC/h and 10 oC/h and holding for 20min) were used to treat

Al-Cu-Li-Sc-Ag alloy, respectively. The microstructures of the treated samples were examined by scanning

electron microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and Transmission Electron

Microscope (TEM), respectively. The mechanical properties of the treated samples were evaluated using the

MTS810 tensile tester.

Results: The effect of enhanced solution treatment on the mechanical properties have been confirmed. The

enhanced solution treatment resulted in the amount and size of the residual phases decreased while the Cu

concentration in IFN-a -Al matrix increased compared with the reference solution treatment process. It shows that

the enhanced solution treatment promoted the dissolution of residual phases and increased the alloying element

concentration in Al matrix. Compared with samples treated with reference solution treatment process, the

enhanced solution treatment processes treated samples have high tensile strength and elongation both using a

heating rate of 60oC/h and 10 oC/h. However, the samples treated with 60oC/h heating rate have higher

mechanical properties compared with that treated with 10oC/h heating rate. Microstructures analysis showed that

the enhanced solution treatment promoted the recrystallization of IFN-a -Al matrix and precipitation of Al2CuLi

precipitate (T1). When using high heating rate, recrystallization of IFN-a -Al matrix of enhanced solution

treatment processes treated samples was restrained. The density of Al2CuLi precipitate (T1) is higher and the

distribution is more even after aged for 24h at 180oC. It shows that the high heating rate not only promoted the

precipitation of Al2CuLi precipitate (T1) and resulted in high dispersion strengthening effect, but also restrained

the recrystallization of IFN-a -Al base and enhanced the refining grain strengthening effect. Both them improved

the mechanical properties of treated samples.

Conclusion: The enhanced solution treatment promoted the dissolution of residual phases and increased the

alloying element concentration in Al matrix, which promoted the precipitation of Al2CuLi precipitate (T1) and

resulted in high dispersion strengthening effect. The samples treated with enhanced solution treatment have high

tensile strength and elongation both using a heating rate of 60oC/h and 10 oC/h compared with samples treated

with reference solution treatment process, especially for that using 60 oC/h heating rate.

Al-Cu-Li-Sc-Ag alloy; enhanced solution treatment; Microstructure; mechanical properties

F-15

Fabrication of high thermal dissipation Al based composites using ultrasonic mechanical coating and

armoring

J. C. Huang 1, W. Y. Tsai1, Guan-Rong Huang1,2, K. K. Wang3, C. F. Chen3

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1. National Sun Yat-Sen University

2. National Center for Theoretical Sciences

3. Metal Industries Research & Development Centre

Aluminum alloys, applied as heat sink, are often inherent with high thermal conductivity but poor infrared

radiation emissivity. Thus high emissivity coating is often added on the Al substrate in decreasing surface

temperature by radiation. In this study, efforts are made in using the ultrasonic mechanical coating and armoring

(UMCA) technique to insert various ceramic combinations, such as Al2O3, SiO2, graphite or carbon nanotube, to

enhance the high efficiency of thermal dissipation. Analytic modeling has also been established in coupling the

thermal radiation and convection on the sample surface into the heat flow equations. Promising match has been

reached between the theoretic predictions and experimental measurements. With proper combinations of ceramic

insertion, temperature of the Al heat sink can be lowered by 5-15oC, highly favorable for applications.

Al composite; radiation emissivity; ultrasonic mechanical coating

F-16

Effects of A-EMS on Microstructure and Mechanical Properties of Eutectic Al-Si-Cu-Mg-Ni alloy

Yang Qiu, Zhifeng Zhang, Mingwei Gao, Yajun Luo

General Research Institute for Nonferrous Metals

Eutectic Al-Si-Cu-Mg-Ni alloys have high strength, high wear resistance, and low thermal expansion coefficients

in wear and elevated-temperature applications. However, the high-temperature properties of the alloys are strongly

dependent on the uniform distribution of alloy elements such as Si and Ni. Coarse structures and serious

segregation in the conventional DC casting process are not avoided. So an advanced melt treatment technology,

namely, the annular electromagnetic stirring (A-EMS) process was developed, by which an intensively shearing

force and a higher shearing rate could be achieved, exhibiting superior grain refinement, remarkable structure

homogeneity, and consequent improved mechanical properties.

In this paper, DC casting process by A-EMS melt treatment was applied, and the effects of annular

electromagnetic stirring and casting processes on grain refinement, homogenization of the Al-Si-Cu-Mg-Ni alloy

were examined. Research result showed that the billets with higher performance, lower segregation, more

uniformly fine solidification structure were obtained in case of A-EMS.

Annular Electromagnetic Stirring; Microstructure; Mechanical Property; Melt Treatment; Al-Si-Cu-Mg-Ni Alloy

F-17

Improved age hardening response of Zn and Cu modified 5xxx series Al alloy

Di Zhang, Cheng Cao, Linzhong Zhuang, Jishan Zhang

University of Science and Technology Beijing

Effect of Zn and Cu additions on the single-step and two-step aging processes of 5xxx series Al alloy have been

investigated by using atom probe tomography and transmission electron microscopy. For the newly developed

alloys, the Mg-Cu clusters are responsible for the rapid age hardening during the single-step aging treatment at

180 ℃ for 1 h, whereas Mg-Zn clusters do not appear. Zn addition dramatically enhances and accelerates the

precipitation hardening response after aging treatment for 1 h. The peak hardness of the alloy is the result of the

synergetic effect of the needle-like S-Al2CuMg and lath-like T-Mg32(AlZn)49 phases. However, with proper

pre-aging treatment at relatively low temperature and subsequently aged at 180 ℃, the precipitation process has

9

been accelerated and enhanced strikingly compared with that of the single-step aging. The microstructure of the

alloy in the peak age condition only consist of high density of equiaxed T-Mg32(AlZn)49 phases with the

S-Al2CuMg phase disappeared.

Al alloy; Precipitation hardening; Cluster; Transmission electron microscopy; Atom probe tomography.

F-18

Characterization of A390 aluminum alloy produced at different slow shot speeds using assisted vacuum

high-pressure die casting

Wenbo Yu1,2, Shoumei Xiong1,2, Zhipeng Guo1,2

1. School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China

2. Laboratory for Advanced Materials Processing Technology, Ministry of Education, Tsinghua University,

Beijing 100084, China

Purpose: Due to high wear resistance, low coefficient of thermal expansion and lightweight hypereutectic Al–Si

alloys have been regarded as the preferred material for engine components Based on the above research discussion,

the present investigation focused on the effect of different slow shot speeds on porosity and size of primary Si

particles in ‘‘plate-shape” castings. Furthermore, the influence of the heat treatment on the mechanical

performance of A390 specimen is also discussed. Compared to other methods, High pressure die casting (HPDC)

belongs to the most cost effective near-net-shape manufacturing process. Recently, it has been observed that

lowering atmospheric pressure in the shot sleeve and die cavity in HPDC could minimize the porosity of the

castings for the subsequent heat treatment processing. The present investigation focused on the effect of different

slow shot speeds on porosity and size of primary Si particles in ‘‘plate-shape” castings. Furthermore, the influence

of the heat treatment on the mechanical performance of A390 specimen is also discussed.

Method: According to the chemical analysis by ICP (Inductively Coupled Plasma), the composition of A390 is

listed in Table 1. The die casting experiment was conducted on a TOYO350t cold-chamber HPDC machine

equipped with a self-improved TOYO vacuum system, as shown in Fig. 1. During the casting experiment, the

vacuum system was launched when the plunger tip moved to the 110mm position in the shot sleeve. Subsequently,

the plunger continued to move at different slow shot speeds (0.05, 0.10, 0.15 and 0.2m/s) until the 270mm

position was reached.

Conclusion: Under different slow shot speeds in vacuum assisted high pressure die casting (VHPDC) process,

plate-shaped specimens of hypereutectic A390 aluminum alloy were produced. According to the results, the

vacuum pressure inside the die cavity increased linearly with the increasing slow shot speed at the beginning of

mold filling. Meanwhile, it was found that the tensile properties of vacuum die castings were deteriorated by the

porosity content. In addition, the average primary Si size varies between 14m, which has a binary functional

relationship with the slow shot speeds. Due to the vacuum effect, the castings were treated by T6 heat treatment.

After heat treatment, microstructural morphologies revealed that needle-shaped and thin-flaked eutectic Si

particles became rounded while Al2Cu dissolved into α-Al matrix. For the as-received sample in-situ tensile test,

microcracks firstly initiate at the primary Si particles and propagated along Al matrix with an transgranular

fracture mode. In contrast, for the treated sample, the crack initiated at the Al2Cu particles and propagated along

Al grainboundaries with an intergranular fracture mode. In-situ three bending test, microcracks firstly formed in

the primary Si particles for both samples. Subsequently, the cracks between primary Si linked along Al grain

boundaries in as received sample. In contrast, the cracks in primary Si linked throung the slid lines in Al matrix.

Furthermore, the fractography revealed that the fracture mechanism has evolved from brittle transgranular fracture

to a fracture mode with many dimples after heat treatment.

10

A390 aluminum, Different slow shot speed; Vacuum assisted high pressure die casting (VHPDC), Si distribution,

Tensile strength, Heat treatment

F-19

The enhanced mechanical properties in an Al-Mg alloy containing nano-laminated structure

Yaojun Lin1,2, Zhibo Liu2, Zhigang Yan2

1. School of Materials Science and Engineering, Wuhan University of Technology, Wuhan, Hubei 430070, China

2. State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao,

Hebei 066004, China

Recently, nano-laminated microstructure has attracted considerable interest due to its ultra-high strength imparted

by boundary strengthening. In this talk, we presented mechanical properties of an Al-Mg alloy 5083

(Al-4.5Mg-0.7Mn-0.15Cr,wt.%) containing nano-laminated microstructures, which exhibits the combination of

high strength and ductility.

The nano-laminated 5083 Al alloy was produced by heavily rolling its fine-grained counterpart to a thickness

reduction ratio of 98% under either room temperature (RT) or cryogenic temperature (CT), followed by annealing

at the temperatures 200 °C and 225 °C. The microstructures of the as-rolled and annealed 5083 Al alloys were

studied using transmission electron microscopy (TEM), transmission electron backscatter diffraction (T-EBSD)

and X-ray diffraction (XRD). Their mechanical properties were measured via tensile testing at room temperature.

The TEM and T-EBSD results show that as-rolled materials are characterized by nano-laminated microstructures

with lamellar width from 20 to 150 nm and the nano-lamellae consist of single-layer cell structure containing

dislocation density of 4 to 7´1014 m-2. After annealing, recrystallization occurred in a portion of lamellae,

forming ultra-fine grains of 100 to 250 nm; the lamellar structure was still retained in the other portion of lamellae,

but cell structure was evolved into subgrain structure with reduced dislocation densities. The XRD results reveal

that most Mg (>4.0 wt.%) was dissolved in the matrix Al. For the as-rolled 5083 Al alloy at RT, the yield strength

is 540 MPa and uniform elongation is 4.5%. After annealing at 200 °C for 3 h, the yield strength is 385 MPa and

the uniform elongation is increased to 10.3%. Furthering increasing annealing temperature to 225 °C leads to an

increase in uniform elongation to 11.5% but a yield strength of 340 MPa. These yield strengths are much higher

than that of the coarse-grained annealed 5083 Al alloy (145 MPa with uniform elongation of 18%). Interestingly,

the as-rolled and annealed 5083 Al at CT can achieve better mechanical properties. In the as-rolled materials, the

yield strength is as high as 615 MPa with uniform elongation of 2.5%, comparable to yield strength and uniform

elongation of nanostructured 5083 Al produced by consolidation of nanostructured powders. After annealing at

200 °C for 3 h, the yield strength is 435 MPa and uniform elongation is9.5%. After annealing at 225 °C for 3 h,

the yield strength is reduced to 375 MPa and uniform elongation is 10.5%.

Based on the microstructures observed, we suggested that the high strength in the rolled plus annealed materials

stems from the signature microstructure: ultra-fine recrystallized grains and nano-laminated structure comprising

nanostructured/ultra-fine sub-grains, which provide strong boundary strengthening. The high ductility can be

attributed to the low dislocation densities and solute atoms, the former providing available space for dislocation

storage and the latter entrapping dislocations intra-granularly, both of which enable dislocation accumulation and

thus improve work-hardening ability.

Al-Mg alloys; Nanostructured materials; Ultra-fine grained materials; Laminated structure; Strength; Ductility.

F-20

Effect of Thermo-mechanical Treatment on Microstructure and Mechanical Properties of AlMg5Si2Mn

11

Alloy Sheets

Yun-Soo Lee, Joon-Hyeon Cha, Su-Hyeon Kim, Cha-Yong Lim, Hyoung-Wook Kim

Korea Institute of Materials Science

Objective: In this study, we focused on evaluating the possibility of applying aluminum casting alloys to wrought

products for easy recycling. The effect of thermo-mechanical treatment on microstructure and mechanical

properties of the aluminum casting alloys was examined.

Methods: The AlMg5Si2Mn alloys, which are used for high pressure die-casting, were prepared via ingot

metallurgical route. The as-cast slabs were homogenized with various conditions. The homogenized slabs were

hot and cold-rolled to final thickness of 1mm. A combination of optical microscopy and scanning electron

microscopy was carried out to characterize as-cast, homogenized, and solution-treated microstructures. Tensile

tests were also carried out to evaluate mechanical properties of AlMg5Si2Mn alloy sheets after T4 and T6

treatments.

Results: Modified homogenization treatment has been demonstrated to improve formability of an AlMg5Si2Mn

alloys by accelerating spheroidization of eutectic Mg2Si particles compared to conventional homogenization

process. The AlMg5Si2Mn alloy sheets were successfully fabricated by hot and subsequent cold rolling after

modified homogenization treatment, and the final heat-treated sheets exhibited enhanced mechanical properties.

Especially, the elongation was 340% higher than that of the as-cast samples. Both the yield and tensile strength

were improved by the combination of homogeneously distributed Mg2Si particles and refined grain size. The

ductility was also increased by reducing grain size and removing casting defects.

Conclusion: The formability and mechanical properties of aluminum casting alloys were remarkably improved by

newly designed thermo-mechanical treatment process, and thus confirm that the possibility of applying aluminum

casting alloys to wrought products. It is concluded that the modified homogenization process may be an effective

method to improve the formability and mechanical properties of aluminum casting alloys without long-time heat

treatment or alloy modification.

AlMg5Si2Mn alloy, Homogenization, Rolling, Microstructure, Mechanical properties

F-21

Fabrication of cellular metals by gas release reaction via powder metallurgical method

Donghui Yang, Lu Jun, Jianqing Chen, Jiang Jinghua, Ma Aibin, Feng Yuan

College of Mechanics and Materials, HoHai University, Nanjing, 2111000

Metallic foam with close pore structures is a class of attractive materials due to their unique combination of

physical, mechanical, thermal, electrical and acoustic properties. Powder metallurgy (PM) route is one of the

attractive methods for metallic production because it allows for processing of wide range components and near-net

shaped geometries foams as well as the foams with integral sandwich structure. Traditionally, the principle of

fabricating a cellular metal fabricated by the PM route is to use a gas from a blowing agent decomposition to form

a cellular structure. And so far, according to this principle, Al/Al alloy can be foamed successfully by adding

titanium hydride (TiH2). In this paper, an idea of taking advantage of the gas release reaction to foam a metal via

PM approach is introduced. Different from the traditional PM route of fabricating cellular metals, the blowing gas

is not from the blowing agent decomposition, but from a gas release reaction, such as a gas release reaction

between an agent and the metal matrix or a gas release reaction between two agents. Finally, several examples of

fabricating cellular metals by using gas release reaction via PM route are presented.

Powder metallurgy, metal foam, blowing gas, gas release reaction.

12

F-22

Production of A Dual Aluminum Alloy with Distinguished Surface Properties by Co-extrusion

Xiang Ma1, Christian J. Simensen1, Rune Østhus2, Ola Jensrud2, Wilhelm Dall1, Arne Nordmark1, Hans J. Roven3

1. SINTEF Materials and Chemistry

2. SINTEF Raufoss Manufacturing AS

3. Norwegian University of Science and Technology

The conventional process route for production of Aluminum products, such as extruded sections, tubes or forged

products is DC (Direct Chilled) casting, followed by homogenization, extrusion, forging and age hardening. For

high-alloyed materials, this process route has its limitations because the solidification during DC casting is so

slow that the material develops large macro-segregations if the alloying content is above 5 – 10 w.t.%. An

alternative to the conventional DC casting process for such alloys is the rapid solidification (RS) process. With

this process, it is possible to achieve a very small-scaled crystalline structure and a homogeneous microstructure

even for high alloyed materials.

To improve the production efficiency of lightweight parts through the combination of multi-materials and forming

technologies, an attempt has been made to examine the possibility to combine the production of RS Al-material

with co-extrusion method for production of a dual material with distinguished surface properties.

Co-extrusion has been successfully carried out by extruding the hybrid billet with RS alloys. The evenness of the

thickness of surface layer is obtained; and a strong bonding between RS and base materials is achieved in order to

avoid the surface defect. Noticeable improvement in corrosion resistance of the hybrid production is also

observed.

Co-extrusion; Rapid solidification; Corrosion resistance

F-23

Effect of deformation parameters on flow behavior and microstructure of Ti-6Al-4V-0.2O alloy

Lin Xiang1, Bin Tang1, Hongchao Kou1, Jie Shao2, Jinshan Li1

1. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an, 710072,

China

2. AVIC Beijing Aeronautical Manufacturing Technology Research Institute, Beijing, 100024, China

Isothermal compressing tests were conducted to investigate the effect of hot deformation parameters on flow

behavior and microstructure of Ti-6Al-4V-0.2O alloy. The experimental results show that the strain rate and height

reduction have no effect on the volume fraction of primary α at a deformation temperature of 860℃. But

compared with the low strain rates(0.01s-1~1s-1) at a deformation temperature of 940℃, the volume fraction of

primary α decreased about 10% at a high strain rate(10s-1). It may be one of the reasons for the significantly

discontinuous yielding phenomenon. Another reason is that the dislocation density decreased suddenly due to the

dynamic recovery. The dislocation density increases with the increasing strain rate and the decreasing deformation

temperature, resulting in the increase of irregular secondary α and the decrease of lamellar secondary α. With

height reduction increasing, the irregular secondary α increases firstly and then tends to be steady because of the

occurrence of dynamic recovery and recrystallization.

Ti-6Al-4V alloy; hot deformation; flow stress; microstructure

F-24

Studies on solid-state phase transformations in titanium alloys

13

Cheng Lin1, Guili Yin1, Aimin Zhang1, Zhiwei Zhao1, Yongqing Zhao2

1. College of Materials Science and Engineering, Liaoning University of Technology

2. Northwest Institute for Nonferrous Metal Research

At present, the studies about the solid-state phase transformation of titanium alloys are still the one of hot topics in

titanium alloy domains. Therefore, the electron structure parameters of muti-element titanium alloys are calculated

with the empirical electron theory (EET) of solids and molecules, and the allotropic transformation, b phase

separation, eutectoid transition, martensitic transformation, and athermal ω formation are investigated in details.

The results are as follows. (1) The allotropic transformation of b to a in titanium alloys can be characterized by the

total cohesive energy of b and a phases as well as by the cohesive energy difference between b and a phases. (2)

The stability of b phase and the separation of b phase can be characterized by the electron structure parameters. (3)

Martensitic transformation in titanium alloy is dependent on the formation and breakup of covalent bonds of

structure units in martensite. The formation and breakup of covalent bonds of structure unit can be characterized

by the bond energy of the strongest covalent bond of the structure unit. (4) The athermal ω formation of titanium

alloys is a result of the atom collapse from the (110) to (111) planes along the direction in β phase. Moreover, the

athermal ω decomposition of titanium alloys is greatly depended on the rigid atom clusters originated from

athermal ω phase, which can be developed to the perfect α phase in virtue of vacancies. (5) The initial formation

concentration of athermal w is related to the first remarkable inflection point of cohesive energy variations. The

calculated cohesive energies can be used to determinate the initial formation concentration of athermal w phase in

titanium alloys in combination with the critical concentration Ck.

titanium alloys; phase transformations; modeling; thermodynamics; electronic band structure

F-25

The solidification behavior and massive gamma tranformation in Ta-cotaining as-cast TiAl-Nb alloy

Keren Zhang, Rui Hu, Jieren Yang

Northwestern Polytechnical University

Abstract: The influence of Ta atoms on the solidification behavior and massive gamma of medium Nb containing

TiAl alloys with the composition of Ti-48Al-3Nb-1Ta is discussed. Through the addition of Ta elements in

Ti-48Al-3Nb alloy, the primary phase transforms from alpha to beta phase during solidification, and the influence

mechanism of Ta on the refinement of dendrites is proposed. Meanwhile, the effect of Ta on massive gamma

transformation is also studied. It can be found that massive gamma phase formed in this work presents a particular

orientation with gamma lamellae which has 120o rotational boundary. It indicates that gamma lamellae can grow

through the existed massive gamma phase due to diffusion-controlled growth. At the same time, two kinds of

gamma laths shown true-twin and peso-twin relationship with massive gamma respectively can be found.

Objective: Ta is considered to be an effective alloy element to improve strength and oxiditation resistence of

TiAl-based alloys. Following suggestion made in many papers that Ta element can refine the microstructure and

promote the massive γ transformation. Therefore, Ta elememt in TiAl-based alloys is needed in increasing the

service tempertautre of TiAl-based alloys. However, characteristics of solidification behavior and massive gamma

phase in cast TiAl-Nb alloys with Ta are still not clear, which is possible technical guidance to identify and

optimize microstructure of as-cast Ta containing TiAl-Nb alloy.

Methods: Alloys with nomnial compositions of Ti-48Al-3Nb and Ti-48Al-3Nb-1Ta (at.%) were selected for

investigation. The raw materials of commercial purity titanium (99.99 wt.%), aluminum (99.99 wt.%), Ti-Nb

binary alloy (52.47wt.% Nb) and Tantalun (99.96 wt.%) were used for preparation the alloys, and the button ingot

14

with a weight of 30 g was obtained by non-consumable vacuum arc melting. To ensure homogeneity, the ingot

was remelted four times. Then samples with sizes of 16×16×16 mm were cut from the ingot. The samples in

ceramic crucibles coated with Y2O3 was held at 1700 oC for 5 min and then followed by air cooling to room

temperature.

Phase constitution of the samples was determined by scanning electron microscopy employing back-scattered

electron mode (SEM-BSE), X-ray diffraction (XRD), transmission electron microscopy (TEM) and Energy

Dispersive X-ray Detector (EDX). Samples for SEM-BSE observation were prepared by standard metallographic

polishing procedures, and Kroll’s etchant was used for etching. Thin foils for TEM observation were prepared by

twin-jet electro-chemical polishing technique using an electrolyte (30 ml perchloric, 175 ml butan-1-ol, and 300

ml methanol) at -30oC and 30 V. The TEM and HRTEM investigations were carried out on a Tecnai F30

microscope operating at 300 kV.

Results: The primary phase of Ti-48Al-3Nb alloy is transformed by Ta from alpha to beta phase during

solidification. The microstructure shows evidence of following solidification pathway: L→ L+alpha→alpha→

lamellae(alpha+gamma) → lamellae(alpha2+gamma) of Ti-48Al-3Nb alloy and L→ L+beta→ L+beta+alpha→

alpha+beta(B2)+massive gamma → lamellae(alpha+gamma) + beta(B2)+massive gamma →

lamellae(alpha2+gamma)+ B2+massive gamma of Ti-48Al-3Nb-1Ta alloy. At the same time, Ta can significantly

refine the dendrites of TiAl-Nb alloys and promote the fomation of massive gamma phase

The γm phase ontained in Ti-48Al-3Nb-1Ta alloy distributs at the boundaries of lamellar colonies. In this alloy,

gamma lamellae can break the irregular boundary of massive gamma phase and makes the boundary parallel to

the lamellae. To obtain detailed information about themassive gamma, further investigation was conducted by

TEM. It can be seen that massive gamma phase is constituted by a large number of defects with various types and

the defects are inhomogeneously distributed. Apart from some parallel dislocations, dislocation walls can be

observed on (211) plane. Unlike the irregular and curved boundary of massive gamma obtained by completely

diffusionless transformation,massive gamma phase formed in Ti-48Al-3Nb-1Ta presents 120o rotational boundary

with gamma lamellae, at which the stacking sequences are both belong to ABC. It indicates that massive gamma

phase can grow through gamma lamellae with a particular orientation due to diffusion-controlled growth.

Furthermore, two kinds of gamma laths can be found marked as gamma1 in massive gamma phase and gamma2 at

the boundary betweenmassive gamma and lamellae. The gamma1 phase obtained by TEM reveals that the

precipitation of gamma1 is determined to be true-twins relationship with massive gamma matrix The gamma2 lath

with defects in it is observed. It presents true-twin relationship with gamma lamellae but pesuo-twin relationship

with massive gamma matrix. The HRTEM image of pseudo-twin interface shows that of gamma2 is paralle to of

the neighbouring massive gamma phase derived from the fast Fourier transform (FFT) images with 60o rotation

relationship, and their stacking sequence of {111} planes is changed from ABC to ACB. The the schematic

illustration of atom structure of the ideal massive gamma, lamellae gamma and gamma2 is presented.

Additionally, EDX results show that composition of Ta in gamma1 and gamma2 are lower than massive gamma

matrix, but Al are higher thanmassive gamma. It can be concluded that Ta had low diffusion coefficients can

stabilize the massive gamma phase, meanwhile, Ta are known to reduce the stacking fault energy and enhance the

mobility of superdislocations, all of which make the dislocations sweep more easily to form twins. Consequently,

massive gamma colonies are observed coexisting with a complex structure of true-twin, 120° rotational interface

and pseudo-twin domains.

Conclusion:

1 The solidification behavior of Ti-48Al-3Nb alloy can be changed by Ta. The primary phase is transformed from

alpha to beta phase by Ta of Ti-48Al-3Nb alloy and Ta can greatly refine the dendrites of TiAl-Nb alloys.

2 In as-cast Ti-48Al-3Nb-1Ta alloy, formation of diffusionless-controlled massive gamma phase is promoted by

15

Ta. The massive gamma phase is accompanied by a remarkable growth of diffusion-controlled gamma lamellae

with a 120o rotational boundary between them.

3 Two kinds of fine gamma laths can form in massive gamma phase. The gamma1 shows true-twin relationship

with massive gamma, and gamma2 shows true-twin relationship with gamma lamellae, peso-twin relationship

with massive gamma phase.

TiAl alloys, Solidification, Ta elements, Massive gamma phase, Twin

F-26

Overview of Titanium R&D in Korea

Yong-Tai Lee

Kyungnam University

Titanium Industry in Korea has ever been developed as the countries economical growth. Those industries

require the various titanium alloys, parts and assemblies, e.g., for the aerospace, military, automobile, marine,

off-shore, desalination, power generation, chemical, sports, leisure, commodities, biomedical, and functional

applications, due to the specific properties of the titanium alloys. It will be presented where the parts are used.

The titanium mill products used in these industries are mostly imported from the foreign countries, together with

some amount of recent domestic production. It is reached up to 13,000 tons of mill products, and about 5,000

tons of sponge, several years ago. However, due to the world economy condition changes the demands are quiet

decreased in this year. The Korean titanium market will be discussed in the point of the import and export

through the years.

The R&D on the various titanium alloy development, processing, evaluations is actively investigated in recent

days by the Industries, Universities, and Research Institutes, for the supporting above mentioned products.

The history and the contents of the R&D in Korea will shortly be reviewed. The more fundamental results will be

presented during this IUMRS-ICA 2016, the 17th International Conference.

Moreover, various research areas, e.g., biomedical implant and orthopedic parts development will be discussed

from the alloy design theory till the test & evaluation, and accreditation procedures. For the industrial

application, several research topics about to reduce the cost, including the low cost alloy design, new alloy

development, and with various processing. A new direct powder reduction process to replace the traditional

Kroll process will be discussed. Furthermore, various attempts to reduce the titanium production cost will be

presented, like low cost alloy investigation, direct powder rolling process, precision casting and forging, together

with defect analysis and elimination procedures, friction stir welding with and without flux. And the fine

powder production for the 3D printing materials.

These will be discussed with the analytical results and theoretical interpretation.

Overview the Statistics, Industrial Application, R&D Programs, R&D Activities

F-27

High cycle fatigue behavior of Ti–5Al–5Mo–5V–3Cr–1Zr titanium alloy

Chaowen Huang1,2, Yongqing Zhao1,2, Shewei Xin2, Wei Zhou2, Qian Li2, Weidong Zeng1

1. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an, 710072,

China

2. Northwest Institute for Nonferrous Metal Research, Xi’an, 710016, China

16

Ti–5Al–5Mo–5V–3Cr–1Zr (Ti–55531) alloy is a relatively new metastable beta titanium alloy based on the

Russian BT22 alloy. Over the last few years, lots of literatures have been conducted to understand the

thermo–mechanical processing, phase transformation, microstructure and properties of the alloy. However, HCF

properties and HCF failure mechanisms of this alloy almost have not been reported. Therefore, it is very essential

to investigate systematically the HCF damage behavior of Ti–55531 alloy.

In this study, high–cycle fatigue (HCF) damage behavior of Ti–55531 alloy with typical lamellar microstructure

(LM) and bimodal microstructure (BM) was studied at room temperature. Fatigue cracks initiation and

propagation mechanisms of the alloy were thoroughly investigated by studying fracture morphology, crack front

profiles, polished microstructural characteristics and dislocation structures beneath fatigue main–crack initiation

sites of HCF samples by SEM and TEM.

The results demonstrate that the BM presents slightly higher HCF strength (107cycles, R=–1, ~ 656 MPa) than

that of the LM (~ 652 MPa). Dislocation analyses indicate that typical dislocation structures include straight

prismatic slip lines, curved dislocation lines, dislocation tangles and twins. Primary alphap particles and

secondary alphas lamellae accommodate more cyclic deformation than retained betar laths. Furthermore, the

appearance of dislocation free zone is observed in the alphap/betatrans boundary of the BM. Fractography

displays that the GB alphaphase has less influence on the HCF behavior of the BM as compared to the LM.

Fatigue microcracks of the LM mainly initiated at the interface of GB alpha films with piror beta grains or

alphas/betar interphases in small–scale (~10μm) heterogeneous microstructure regions (SHMRs). Microcracks

primarily nucleated at alphap/betatrans interfaces and alphap particles interiors in the BM. Moreover, a small

amount of microcracks initiated at alphas lamellae in SHMRs of the LM and alphas platelets in the BM. The

combination of transgranular and intergranular crack propagation was observed in these two microstructures.

Crack front profile of the LM presented much rougher than that of the BM.

Not only GB alpha films at prior beta–GBs, but also SHMR in prior beta grain interiors are weak microstructure

features in the LM, which strongly affect the HCF behavior of the alloy. In constrast, the GB alpha phase has less

influence on the HCF behavior of the BM. Moreover, the alphap particles play a key role in promoting the

initiation and propagation of cracks in the BM. Therefore, it is reasonable to conclude that fatigue crack nucleated

more easily in the LM than in the BM, which resulted in slightly lower HCF strength in the LM than in the BM of

Ti–55531 alloy.

Ti–55531 titanium alloy; microstructure; high–cycle fatigue; crack initiation; crack propagation

F-28

The high cycle fatigue behaviours of TC21 titanium alloy with different microstructure

changsheng Tan1, Qiaoyan Sun1, Lin Xiao1, Yongqing Zhao2, Jun Sun1

1. State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University

2. Northwest Research Institute of Nonferrous Metals, Xi'an, Shaanxi

High-cycle fatigue behavior of an a/b titanium alloy, Ti–6Al–2Sn–2Zr–3Mo–1Cr–2Nb–0.1Si (TC21) with

different microstructure, such as as received microstructure, bimodal microstructure (BM) and full lamellar

microstructure (LM), was investigated at room temperature. Cyclic fatigue life, slip characteristics and crack

nucleation were systematically analyzed. The results show that the LM possesses the highest high-cyclic fatigue

property, followed by BM, and the as received microstructure is the worst. The BM microstructure possesses

better combination of high strength and ductility and but lower high-cycle fatigue life than those of the LM one,

which indicates that the microstructure plays a highly signicant role in high-cycle fatigue crack nucleation in

addition to the eect of tensile strength. The resistance of the LM against fatigue-crack initiation was superior to

17

that of the other microstructure, which is attributed to the effects of a phase morphology and deformation

homogeneity. For bimodal microstructure (BM), the nonuniform plastic deformation existed within the different a

morphology phase, such as primary equiaxed a, primary lath a phase and secondary a in btrans. Dislocations

nucleated and annihilated at different a/btrans interfaces, and promoted strain concentration loading to fatigue

microcracks initiation at lower fatigue cycles. However, uniform a phase with similar morphology and size exists

in lamellar microstructure (LM) that can deform homogeneously under high cycle loading, which delays the

initiation of fatigue crack.

TC21 titanium alloy; Different microstructure; High–cycle fatigue; Dislocation slip; Fatigue crack initiation

F-29

The pre-strain hardening in microscale pure titanium

Wenjuan Kou, Qiaoyan Sun, Lin Xiao, Jun Sun

State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, P. R. China

Absract: The aim of this research was to investigate the deformation behavior of single crystal Ti micropillars with

compression direction, an orientation favorable for double prismatic slip. Results show that deformation twinning

becomes prevalent in the larger micropillars after pre-strain besides the as-expected double prismatic slip. The

occurrence of deformation twinning can be explained on the basis of the assistance of dislocation pile-up and the

Saint-Venant’s principle, respectively. Detwinning occurs in the re-compression process. The mechanism of

detwinning can use twin boundary migration model to explain. The pre-strain hardening is significant in larger

pillars and also has a size effect due to the appearance of deformation twinning formed in pre-strain process.

Dislocations are pinned at the twin boundaries which exist as the barriers to hinder the movement of dislocations.

This study develops the understanding on the mechanisms of pre-strain hardening and can contribute to the future

development of advanced structural materials.

Titanium; Micropillar; Pre-strain hardening; Deformation twinning; Detwinning

F-30

Effect of forging processes on microstructure and mechanical properties of high temperature titanium alloy

containing erbium

Zhenqiang Wang, Bolong Li, Tongbo Wang, Zuoren Nie

Beijing University of Technology

In this paper, a new high temperature titanium alloy containing erbium was designed. The influence of α+β

forging process and β forging process on microstructure and mechanical properties of the alloy were studied. The

microstructure characteristic of the new high-temperature titanium alloy after different forging processes were

observed via optical microscope (OM) and scanning electron microscope (SEM). The major mechanical

properties, such as tensile strength and fracture toughness, were detected. And the fracture morphologies were

analyzed by means of SEM and energy dispersive spectroscopy analysis (EDS). The results showed that the

forging process significantly affected the microstructure of the alloy. The alloy exhibited nearly equiaxed

microstructure and lamellar microstructure after α+β and β forging, respectively. In addition, there were Er-rich

phases in both forged alloys. The alloy with nearly equiaxed microstructure acquired a good comprehensive

performance. However, the alloy with lamellar microstructure had higher strength and less toughness. The tensile

fracture of the alloy after α + β forging had more dimples, while cleavage plane was obvious in the alloy after β

forging. Owing to the addition of erbium and the formation of Er-rich phases, the forged alloys possessed

18

excellent strength, especially the strength at high temperature, which was better than most of the existing high

temperature titanium alloys. But the Er-rich phases might be the main reason for fracture, resulting in relatively

poor plasticity at high temperature.

forging process, microstructure, mechanical properties, Er-rich phase

F-31

Effect of rare earth Er on the microstructure and mechanical properties in high temperature titanium

alloys

Bolong Li, Tongbo Wang, Peng Han, Zhenqiang Wang, Zuoren Nie

Beijing University of Technology

The high temperature titanium alloy containing Er, i.e. Ti-6Al-2.5Sn-4Zr-0.3Mo- 1Nb-0.35Si-xEr (x=0, 0.1,

0.3wt%), were prepared by using Vacuum Arc Remelting (VAR) furnace. The microstructure of cast alloys was

typical lamellar microstructure. Both the grain size and lamellar structure inside grains were significantly refined

with addition of the Er. The billet was forged in beta phase, and then forged in two phase region. After forged, the

alloys were heat treated in the condition of 1020℃/1h/AC+750℃ /2h/AC. Two type of microstructure were

obtained after heat treatment, i.e. lamellar and duplex microstructure. There were no silicide precipitate after

solution treatment, but the silicide increased after aging treatment, and less silicide precipitated in the beta phase,

but in the boundary of lamellar alpha phase. Also less Ti3Al phase precipitated in the alloys after aging treatment.

After subjected to 600℃ /100h thermal exposure, the Ti3Al phase with size of 5nm to 10nm was precipitated

homogeneously in α lamellar. The spacing between the Ti3Al particles was about 10nm. Specimen containing

Er shows excellent creep properties under the condition of 600℃ /100h/150MPa. It is suggested that the silicide

and Ti3Al phase that pin up dislocations strongly were precipitated in the alloys during creep procedure, and the

second phase containing Er reduced the amount of beta-stabilizing solution element in surrounding matrix, thus it

increased the content of Si solution in the matrix.

Titanium alloy, rare earth Er, microstructure, mechanical property

F-32

A new phase transformation mechanism for homogeneous precipitation of Ti1023 in the absence of the

ω-phase

Pei Li, Qiaoyan Sun, Lin Xiao, Jun Sun

State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University

Generally the presence of precursory metastable ω precipitates promotes a homogeneous intra-granular

distribution of ne intragranular α precipates in the absence of the ω-phase when the alloy is step-quenched below a

critical temperature. We have investigated the mechanisms responsible for the β to α phase transformations at

certain temperature. These precipitates are associated with a sudden, signield method to assist in viewing the

detail and notion of the process. A process with structure and chemistry changes occurring asynchronous has been

suggested.

Ti-1023;ω precipitates;homogeneous precipitation;phase field method

F-33

Precipitation behavior of secondary α phase during continuous heating in a hot-rolled near β titanium

Ti-7333 alloy

19

Jinshan Li, Shubo Liu, Bin Tang, Hongchao Kou

State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, PR

China

Near-beta titanium alloys are a promising candidate for manufacturing fasteners in aerospace and automotive

industries due to their high yield strength, low density and good fatigue and crack resistance. And a range of

combination of mechanical properties of the alloys is very sensitive to alpha precipitate in beta matrix, including

its size, morphology, volume fraction, geometrical arrangement and orientation. In this work, dilatometer is

applied on the beta-quenched Ti-7333 alloy to investigate the precipitation dynamics of secondary alpha phase

during continuous heating process. Meanwhile, the corresponding continuous heating experiments are conducted

on beta-quenched specimens as well. And the precipitation behavior of secondary alpha phase during continuous

heating process, including the nucleation process, morphologies evolution, and orientation relationship of alpha

phase with respect to adjacent beta matrix, is characterized by scanning electron microscopy (SEM) and

transmission electron microscopy (TEM) techniques. The results indicate that the temperature range of

precipitation for alpha is about 450 oC. The alpha with the dot-like morphology precipitate firstly, then the

dot-like alpha connect to form a acicular-like morphology as the temperature increases. The various geometrical

arrangements of alpha are presented in beta matrix, which is closely related to the occurrence of variant selection

of alpha. The volume fraction of alpha increases with increasing of temperature, then, the volume fraction

decreases with increasing temperature.

Near-beta titanium, Continuous heating, Secondary alpha, Variant selection

F-34

The Effect of Annealing on Microstructure and Tensile Property of Cast TG6 High-TemperatureTi-Based

Alloy

Lang-ping Zhu1,2, Jian-chong Li1,2, Hai Nan1,2, Xiao-fei Mo1,2,3, Qian Luo1,2

1. Beijing Institute of Aeronautical Materials

2. Beijing Engineering Reaserach Center of Advanced Titanium Alloy Precision Forming Technology

3. BAIMTEC MATERIAL CO., LTD.

Annealing experiments were carried out on TG6 Ti-Based alloy, which was prepared by investment casting. The

microstructure and room temperature tensile properties were studied. The results showed that the as-cast alloy has

a structure of widmanstatten with coarse grains, and the plasticity is only 0.8%. While the plasticity reached 3.7%

after hot isostatic pressing under 900℃. Annealing treatment was carried out at 750℃，and the ductility improved

to up to 5%, while the tensile strength didn’t change obviously, the tensile fracture of the alloy showed cleavage

fracture after tot isostatic pressing and heat treatment, and no metallurgical defects were found, while it was find

out that silicide phase (TiZr)6Si3 precipitated after annealing treatment .

TG6; cast; annealing; microstructure; tensile properties

F-35

Spark plasma semi-solid sintering: Bi-modally grained high yield strength and ductility Ti-based alloys

based on the eutectic transformation

Limei Kang, Chao Yang

National Engineering Research Center of Near-net-shape Forming for Metallic Materials, South China University

of Technology, Guangzhou, China

20

Bimodal microstructure was successfully prepared by mechanically milling quinary Ti-Nb-Fe-Co-Al powder and

subsequent spark plasma semi-solid sintering. The bulk alloy exhibits a novel bimodal microstructure composed

of a ultrafine lamellar and ellipsoid eutectic (from 150nm to 1μm) and micron-sized(~5μm) minor phase embed in

the eutectic matrix, which differs distinctly from other bimodal or multimodal microstructures reported so far.

As-sintered bulk alloy exhibits a high strength of 2897 MPa with 23% ductility, especially yield strength up to

2050 MPa. The mechanical property also superior to published values of equivalent materials so far. This unusual

combination of strength and ductility is attributed to a mechanism that involves the blocking, branching and

multiplication of the bcc β-Ti lamellae and the interactions with dislocations in the bcc Ti(Fe, Co) lamellae as well

as on the stability of a coherent interface. By designing phase proportion of eutectic reaction, or the content of

eutectic reaction-induced liquid phase, we can tailor microstructure and mechanical property of semi-solid

sintered bulk alloys by designing proper alloy composition. The novel idea provides some inspiration for

fabricating nano-grain or bimodal microstructure with better fascinating combinations of properties in high

melting point alloy systems by spark plasma sintering.

Spark plasma sintering (SPS), Semi-solid, Eutectic, Bimodal structure, Ti-based alloys, Mechanical alloying

F-36

R&D of New Ti-alloys Used for Shipbuilding

Yongqing Zhao

Northwest Institute for Nonferrous Metal Research

Because of their excellent comprehensive properties, such as excellent corrosion properties in sea water, good

match among mechanical properties, processing technology and welding properties, Ti and its alloys are the ideal

structural metal materials used for shipbuilding.This paper reviews the R & D of new titanium alloys used for

shipbuilding which developed in China, such as Ti75 alloy, Ti31 alloy, Ti80 alloy, Ti91 alloy and Ti-B19 alloy.

Ti75 is a middle strength and high toughness Ti alloy. Ti31 is a middle strength and high plasticity Ti alloy. Ti80 is

a high strength and high toughness Ti alloy. Ti-B19 is super high strength and high toughness Ti alloy. This paper

also shows the applications of these new alloys.

Ti alloys; Ti alloys used for shipbuilding; mechanical properties; corrosion rate

F-37

Tailoring precipitates for ultra stable plasticity in submicron Ti alloys

Yan Pan, Qiaoyan Sun, Lin Xiao, Jun Sun

State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University

Titanium and its alloys have a great potential application in micro-electromechanical systems (MEMS) due to

superior strength and fracture toughness combined with excellent corrosion resistance. The strength of the

titanium alloys demonstrate a significantly increase in submicron scales due to the "size effect". However, plastic

instabilities including strain burst or stress drop often occur in these scales resulting from the generation and

escape of avalanche-like dislocations. Here, we discover that extraordinary stable plasticity and superior yield

strength are simultaneously achieved in the titanium alloy pillars which possess a large number of high densities

of nanoscale athermal ω (ωath) precipitates. A statistical analysis of stress drops shows Poisson fluctuations in all

pillars with ωath precipitates, which indicates small slip events or thermal activation progress. It is attributable to

the existence and transition of ωath precipitates from one variant to another. The ωath variants transition is prior to

dislocation cutting them, which can forming dense slip bands and resulting in a stable plastic deformation.

21

Therefore, a combination of stable plasticity and superior strength makes this type of alloy with ωath precipitates

is viable in the application of fabricating micro-electromechanical components or systems.

Stable Plasticity; Pillars; athermal ω precipitates; Variants transformation

F-38

Effect of boron on the hot deformation behaviors of Ti-2Al-9.2Mo-2Fe alloy

Rong Chen1, Songxiao Hui1, Wenjun Ye1, Dong-Geun Lee2, Yongtai Lee3

1. General Research Institute for Nonferrous Metals

2. Sunchon National University

3. Kyungnam University

Hot deformation behaviors of Ti-2Al-9.2Mo-2Fe alloy with boron were investigated in a hot compression test at

temperatures ranging from 850 to 1000oC and strain rates ranging from 0.01 to 10s-1. With decreasing strain rate

and increasing deformation temperature, dynamic recrystallization was promoted in both alloys. The nucleation

mechanism of dynamic recrystallization involved grain boundary bulging and sub-grain rotation. In case of

deformation at low temperatures and high strain rates, the boron-free alloy only showed dynamic recovery

phenomenon. However, due to the particle-stimulated nucleation mechanism of recrystallization by TiB particles,

the boron-containing alloy showed dynamic recrystallization at that condition. These dynamic recrystallization

grain nuclei were formed by lattice rotation and subgrain growth from deformation zone in the initial grains,

which were close to the TiB particle. Moreover, the flow stress of the boron-containing alloy was lower than that

of the boron-free alloy due to the grain refinement during hot deformation process.

New beta titanium alloy; Boron addition; Hot deformation; Particles stimulated nucleation; Dynamic

recrystallization

F-39

Slip transmission behavior at alpha/beta interfaces and model of strengthening evaluation in TC21 alloy

Qiaoyan Sun, Changsheng Tan, Lin Xiao, Jun Sun

Xi'an Jiaotong University

In present work different slip transmission behaviors at a/β interphase in TC21 alloy and strengthening

mechanism from a/β interphase are discussed with respect of existence of the second acicular alpha phase in order

to put forward a strengthening evaluation model for TC21 alloy. The alloy with duplex microstructure were

subjected to solid solution treated at 900°C for 4.5 hours to get coarse a phase and plate-like β phase, and another

group of sample were annealed at 600°C to nucleation second acicular a phase in plate-like β phase. The dog-bone

tensile sample were polished and etched before tensile tests so that the slip bands in a and β phase can be observed

clearly. The results show that slip starts in a phase and with increasing strain the slip band go cross the a phase.

Whether the slip bands penetrate a/β interphases depends on the existence of second a phase in plate-like β phase.

The slip can penetrate a/β phase easily and reactive slip in beta phase when there is no second a in beta phase,

while slip stop at a/β phase when second acicular a existence in β phase. As a result, the latter interphase brings

about strengthening for titanium alloy. The slip systems are prismatic slips in (10-10) prismatic plane in a phase

and slip in (111) plane in beta phase. Twinning is activated in beta phase with second acicular a phase to relax the

stress concentration at interphase which can avoid formation of crack at interphases. The evaluation of

strengthening is conducted on basis of dislocation pile-up at a/β interfaces

TC21 alloy, slip transmission, strengthening

22

F-40

A self-adjusting strengthening method by nano martensitic Transformation in Ti2448 Single Crystal

Submicro-pillars

Mingda Huang1, Lin Xiao1, Qiaoyan Sun1, Yunzhi Wang2, Jun Sun1

1. Xi'an Jiaotong University

2. Frontier institute of science and technology , Xi'an Jiaotong University

As a classical hardening method, secondary-phase strengthening has been studied for decades to extend the

application of materials, especially some “soft” light metals such as Al, Mg, Ti and so on. The strengthening effect

of secondary-phase strengthening is strongly influenced by three factors of secondary phase: (i) morphology, (ii)

phase boundary, (iii) distribution. J. F. Nie [1] and F. P. Yuan et al. [2] reported that the shape and dimension of

secondary phase have deep influence on strengthening. Additionally, the uniform distribution of secondary phase

particles is the key to preserve the plasticity in the process of strengthening matrix [3]. Therefore, many complex

processes and crafts costing a lot have been designed to ensure appropriate morphology, good phase boundary and

uniform distribution of strengthening particles at the same time in industrial manufacture. To simplify processes

and reduce cost, It is extraordinary meaningful to find a phase transformation mechanism whose product phases

satisfy the three factors at the same time. Stress induced martensitic transformation (SIM) is widely used not only

in TRIP as an efficient secondary phase strengthenging mechanism [4], but also in Shape Memory Materials as a

self-recovery mechanism [5]. The present paper reports a self-adjusting strengthening method by stress induced

nanoscale martensitic (SINM) transformation to introduce nanoscale, dense and uniform distributed strengthening

particles with coherent phase boundary. Ti2448, a kind of meta-stable Ti alloy, can be efficiently strengthened to

approach ideal strength in micro-pillars by combining stress induced nanoscale a'' martensitic transformation and

size effect. As a self-adjusting and uniform deformation mechanism, the stress induced nanoscale martensites can

undertake more external stress and strain when dislocation slip is depressed by size effect in micro- and

submicro-pillars.

Stress induced nano-martensitic transformation, nano-pillars, size effect

F-41

The twinning behavior of Ti-xV(x=2,4,8) alloys under quasi-static and dynamic deformation conditions

Qiaochu Wang

General Research Institute for Nonferrous Metals

The quasi-static and dynamic mechanical response of Ti-xV(x=2,4,8) alloys was obtained using MTS universal

testing machine and spilt Hopkinson pressure bar by means of compression, and the deformed microstructures

were observed by EBSD. The strain rate and element V content were two parameters designed to study

mechanical properties and twinning deformation rules under quasi-static and dynamic deformation conditions by

analyzing mechanical response and microstructure evolution. EBSD technique was applied to confirm twinning

types in quasi-statically and dynamically deformed structures with ε=0.25. By combining the calculated Schmid

factor values of grains with or without twinnings with Schmid distribution images of {10-12}, {11-21} and

{11-22} types of twinning, Schmid factor was proved to be a crucial parameter determining the activation of

twinning in Ti-xV(x=2,4,8) alloys. According to critical Schmid factor values and stress with ε=0.25, the critical

stress condition needed by {10-12}, {11-21} and {11-22} types of twinning activation can be calculated under

quasi-static and dynamic deformation conditions. The result shows that increasing the strain rate does restrain the

23

twinning behavior in Ti-xV(x=2,4,8) alloys. Furthermore, the addition of element V content ranged from 2wt.% to

8wt.% enhances the twinning restrained effect to some extent.

Quasi-static, Dynamic, Twinning behavior, Element V content

F-42

Hot deformation behavior and ring rolling process of Ti-22Al-24Nb-0.5Mo powder metallurgical preform

prepared by hot isostatic pressing

Zhengguan Lu, Lei Xu, Jie Wu, Xiaoxiao Cui, Rui Yang

Institute of Metal Research, Chinese Academy of Sciences

Ring rolling process is one of the most important and necessary deformation processes to prepare Ti2AlNb

components with large size. In this article, Ti-22Al-24Nb-0.5Mo (at. %) ring billets were prepared by a typical

powder metallurgy (PM) route. Hot isostatic pressing (HIP) promoted the densification of pre-alloyed powders,

and this PM route was considered as a potential alternative route in preparing Ti2AlNb preform. Hot compression

tests were conducted to study the hot deformation behavior of Ti2AlNb PM alloy, and two rectangular rings

(r=200~355mm, height=160) were rolled as a validation experiment. Results show that the flow stress of Ti2AlNb

alloys exhibited a significant drop at the very beginning of the deformation, and became stable with increasing

strain. The stress-instability behavior was more obvious when the deformation temperatures were near to the

Ti2AlNb phase transition temperature or the strain rates became large. The reason for the sharp fluctuation of flow

stress at the initial stage of deformation is related with the phase transformation which is very sensitive to

environment temperature and thermal mechanical deformation. Processing windows during initial stage of ring

rolling process is very crucial, and failure control is much difficult to for Ti2AlNb PM alloy. By using the

improved heat preservation method and optimized rolling parameters, a sound Ti2AlNb PM rectangular ring billet

was successfully rolled to 60% deformation in 2 passes.

Ti2AlNb alloy; powder metallurgy; hot isostatic pressing; ring rolling; deformation behavior

F-43

Microstructure and mechanical properties of hot-isostatically-pressed Ti-5Al-2.5Sn ELI powder compact

Ruipeng Guo1,2, Lei Xu2, Jiafeng Lei2, B.Y. Zong3, Rui Yang2

1. School of Materials Science and Engineering, Northeastern University, Shenyang 110819, China

2. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110819, China

3. Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University,

Shenyang 110819, China

Hot isostatic pressing (HIPing) is an accepted method for the manufacturing of selective near-net shaping powder

components. In this work, Ti-5Al-2.5Sn ELI alloy parts have been was prepared by HIPing from gas atomized

powder. The effect of powder pre-treatment on the microstructure and mechanical properties of HIPed

Ti-5Al-2.5Sn ELI powder compacts was investigated. The results showed that the powder size has a little

influence on the tensile properties of HIPed powder compact. The room temperature tensile strength increases

with the oxygen content, and the correlation between the oxygen content and tensile strength was established.

With optimized pre-treatment, the HIPed samples were found to show the mechanical properties comparable to

those as-forged and annealed samples.

Ti-5Al-2.5Sn ELI; Powder metallurgy; Hot isostatic pressing; Near net shaping

F-44

24

Numerical and Experimental Study on the Counter-gravity Casting of Nb-containing Gamma TiAl Alloy

Kuan Wang, Jieren Yang, Jinshan Li, Rui Hu

Northwestern Polytechnical University

Nowadays, TiAl alloys become one of the high temperature structure materials with unlimited potentialities due to

excellent high temperature performance and physical properties. In order to overcome TiAl alloy’s forming

difficulty and high thermal stress in casting process, on the basis of counter-gravity casting and temperature

control solidfication ,this paper investigates microstructures of as-cast Ti-48Al-2Cr-2Nb alloys with differernt

geometrical shape and size via cold crucible melting and counter gravity casting

technology.

The results show that, the limit thickness of TiAl alloy can reach 0.5 mm. As the casting bar’s diameter turns

from 3 mm to 20 mm, the cooling rate of the same cross section shows great difference which leads to

microstructure inhomogeneity and great themral stress。In addition, we also investigate how the temperature fields

change with the method of numerical modeling and put forward the method to enhance alloy’s flowability,

improve microstructure homogeneity and reduce microsegregation.

TiAl alloys; Counter-gravity casting; Numerical modeling; Microstructure

F-45

Effect of Solution Treatment on the Microstructure Development of TC18 Alloy

Zhimin Hou 1,2

1. Northwestern Polytechnical University

2. Northwest Institute for Nonferrous Metal Research

In order to obtain ideal basketweave of TC18 (Ti-5Al-5Mo-5V-1Cr-1Fe) through beta heat treatment combined

with common alpha + beta solution heat treatment, the microstructure development of TC18 titanium alloy

subjected to various duplex solution treatments was analyzed. The sample was firstly carried out in 870°C(above

beta transus temperature) for 1 hours followed by FC, AC, WQ separately, then was solution treated in top of

alpha/beta region, and then furnace cooling to low temperature for 1h followed by AC. Varying the cooling rates

of beta solution heat treatments can significantly influence the microstructure of alpha phase followed by same

duplex solution heat treatment. Higher cooling rate resulted in tiny and homogeneous alpha phase, for which the

length-width ratio is nearly to 1, and harmful for damage tolerance. However, for exceeded slow cooling rate, the

low density and overlarge length-width ration alpha lath was the dominant morphology. For the item of obtain

perfect alpha lath in proper ration, the cooling rate should be limited in narrow window. For the second step of

solution heat treatment, the density and length-width ration of alpha phase was mainly controlled by first high

alpha/beta heat treatment temperature, and the percent and dimension of it was by second low alpha/beta heat

treatment temperature. Second alpha/beta heat treatment temperature significantly influenced the heat treatment

response of the microstructure. High heat treatment temperatures promoted greater amounts of retained beta with

fine, transformed alpha in the final microstructures. Lower alpha/beta heat treatment temperatures promoted

retained beta microstructures which were less responsive to aging heat treatment. And the higher amount of fine,

secondary alpha phase promoted higher strength and lower toughness. So the balance of tensile strength and

ductility can be controlled by the second alpha/beta solution heat treatment temperature combined with ageing

heat treatment. The density and length-width ration of alpha phase were controlled by beta solution heat treatment

cooling rate and temperature of first high alpha/beta heat treatment, which were the crucial factors for fracture

toughness. By precise design the heat treatment process factors, the fracture toughness, strength and ductility of

25

TC18 alloy can matches well. The typical heat treatment process is 870℃/1h,AC+820℃/1h,FC to 740℃

/1h,AC+600℃/1h,AC.

TC18, duplex solution treatments, basketweave

F-46

Experimental Determination of Thermophysical Properties of Liquid and Solid Binary Ti–Si Alloys

Kai Zhou, Peng Lu, Wenxin Hou, Bingbo Wei

Northwestern Polytechnical University

It is usually difficult to obtain substantial undercooling of liquid alloys, especially for Ti-based alloys due to their

high chemical reactivity. This results in a serious scarcity of information on their thermophysical properties in the

metastable undercooled state. Here, electromagnetic levitation technique was applied to investigate the liquid

undercoolability and thermophysical properties of binary Ti-Si alloys. Maximum undercoolings of 234 K (0.13TL)

and 327 K (0.20TL) were achieved for liquid Ti-5at.%Si and Ti-13.5at.%Si alloys, respectively. On the basis of

high undercooling, the surface tension and specific heat of liquid Ti-Si alloys were separately determined by

oscillating drop method and drop calorimetry over wide temperature range. The viscosity and density of

undercooled liquid Ti-Si alloys were calculated by some well-known models using the measured data as input.

Moreover, the eutectic solidification of Ti-Si alloys were studied through XRD, SEM and EDS analyses. In

addition, the thermal diffusivity and thermal conductivity of solid Ti-Si alloys were also determined by laser flash

method，and the measured results were significant change in the experimental temperature range.

Ti-Si alloy, high undercooling, surface tension, specific heat, thermal diffusivity

F-47

Different Precipitation Behaviors and Mechanical Property Heterogeneity of an Extruded

Mg-7Y-1Nd-0.5Zr (wt.%) Alloy Bar with Cross-section of 230×140mm

Guoliang Shi, Kui Zhang, Xinggang Li, Yongjun Li, Minglong Ma, Jiawei Yuan

State Key Laboratory for Fabrication and Processing of Non-Ferrous Metals, General Research Institute for

Non-Ferrous Metals, Beijing 100088, China

Different precipitation behaviors and mechanical property heterogeneity of a Mg-7Y-1Nd-0.5Zr (wt.%) (WE71)

alloy bar with cross-section of 230×140mm were investigated by hardness test, tensile test, transmission electron

microscopy (TEM) and X-ray diffraction (XRD) macro-texture measurement. The WE71 bar was industrially

manufactured by “multi-direction forging (MDF) + extrusion + on-line water quenching + T5 aging” technique.

T5 aging treatments at 200 and 235℃ exhibit totally different age-hardening behaviors. During aging at 235℃,

the hardness only has a slight increase during the first 100h: 77HBS (0h)→81HBS (10h)→82HBS (75h)→87HBS

(100h). However, during aging at 200℃, the hardness shows remarkable increase during the first 100h: 77HBS

(0h)→83HBS (10h)→113HBS (75h)→110HBS (100h). TEM analysis reveals that: (1) after 100h aging at 200℃,

fine β′ precipitates uniformly disperse within the matrix with a relative high number density which is about 40

times higher than that of sample subjected to 235℃/100h aging, and the size of each β′ block is about 10×

10nm viewed from [0001]α, moreover, bridging structures connecting β′ blocks have appeared; (2) after

100h aging at 235℃, β′ precipitates about 40nm in size arrange themselves into sparsely-distributed chains

and broad precipitate free zones are remained among these chains, which severely weakens the precipitation

strengthening effect; (3) after 10h aging at 235℃, β′ nucleus intend to nucleate on dislocations, and such

dislocation nucleation closely relates to the chain-like arrangement of β′ precipitates. XRD macro-texture

26

results show that WE71 bar has much weaker basal texture as compared with a Mg-8Al-0.5Zn-0.15Mn (wt.%)

(AZ80) bar. The maximum basal texture intensities in the outer (O) and center (C) of WE71 bar are all about 3,

however, those of AZ80 bar are 17 and 14, respectively. Tensile tests have been performed on as-aged (T5-200℃

/48h) WE71 samples cut from O and C along ED, transverse direction (TD) and normal direction (ND), and the

stress-strain curves of all these samples demonstrate the same curve shape in the yielding stage (YS) which

implies a plastic mechanism dominated by slipping rather than twinning. The WE71 bar has obvious mechanical

property heterogeneity between O and C. When stretching at RT, sample along ED in O (ED-O) has the best

tensile properties, i.e. YS (RP0.2), ultimate tensile strength (Rm) and elongation (A) are 246MPa, 368MPa and

5%, respectively, yet ND-C sample has the worst properties, i.e. RP0.2, Rm and A are 194MPa, 255MPa and 2%,

respectively. When stretching at 200℃, it is interesting that RP0.2 do not decrease but slightly increase as

compared with results of RT stretching, e.g. RP0.2, Rm and A of ND-C sample are 225MPa, 263MPa and 3.5%.

According to the results obtained, it can be concluded that RT mechanical properties of WE71 alloy can maintain

for a long time at 200℃, but will degenerate rapidly as the temperature rises to 235℃.

Mg-Y-Nd; wrought magnesium alloy; mechanical property; precipitation; texture

F-48

Effects of Zn addition on second phases and mechanical properties of Mg-8Al-2Sn wrought alloy

Luyao Jiang1,2, Dingfei Zhang1,2, Chen Rong1,2, Fei Guo1,2, Hansong Xue1,2, Junyao Xu1,2, Fusheng Pan2,3

1. Chongqing University

2. National Engineering Research center for Magnesium Alloys

3. Chongqing Academy of Science & Technology

Magnesium (Mg) alloys have received an increasing interest in the past decade for potential applications in the

automotive, aircraft, aerospace and electronic products. However, the widespread use of Mg alloys has been

limited by its insufficient strength. In previous studies, AZ80 (Mg-8Al-0.5Zn-0.3Mn, wt.%) alloy which has

become one of the prominent developed wrought Mg alloys as heat treatable alloys can be strengthened by Sn

element. AZ80-2 wt.% Sn extruded alloy after solid solution and aging treatment showed well mechanical

properties. To understand the effect of Zn in the alloy and optimize the Zn content, microstructure and mechanical

properties of Mg-8Al-2Sn-(0-1) Zn wrought alloys are analyzed. Phase diagram and X-ray diffraction were used

to analyze the phase transformation. Images of optical microscopy (OM) and scanning electron microscopy (SEM)

were performed to show the microstructure of the alloys. Transmission electron microscopy (TEM) were used to

identify the habit plane and the direction relationship between second phases and the matrix. Vickers hardness and

tensile tests were measured as mechanical properties of the alloys. The results indicated that Zn segregated to the

Mg17Al12 phases and formed Mg17(Al, Zn)12 phases which have the same structure with Mg17Al12. Although

the lattice constant of Mg17(Al, Zn)12 phases decreased, the habit plane and the direction relationship of

continuous precipitation remained the same. With the addition of Zn, the density of both discontinuous

precipitation and continuous precipitation Mg17(Al, Zn)12 phases increased due to the increase of nucleation rate.

Precipitation rate and fraction of discontinuous precipitation Mg17(Al, Zn)12 phases increased. There is no

obvious effect on Mg2Sn phases and Mg2Sn phases maintained fine and dispersive. Due to precipitate compact

second phases during aging treatment in Mg-8Al-2Sn-1Zn alloy, the mechanical properties were outstanding in

this alloy. The yield strength, ultimate tensile strength and elongation were 296 MPa, 408 MPa and 7% in as-aged

Mg-8Al-2Sn-1Zn alloy which were higher than the Zn-free alloy and had the increment by 34 MPa (for yield

strength), 42MPa (for ultimate tensile strength) and 1% (for elongation), respectively.

Mg alloy, aging treatment, second phase, Zn

27

F-49

Constitutive modeling of distortional hardening for wrought Mg alloys based on internal state variables

Baodong Shi1, Yan Peng1, Chong Yang1, Fusheng Pan2

1. Yanshan University, School of Mechanical Engineering, National Engineering Research Center for Equipment

and Technology of Cold Strip Rolling

2. Chongqing University, National Engineering Research Center for Magnesium Alloys

The anisotropic mechanical behavior of AZ31 extrusion bar was tested by means of tension-torsion biaxial tests.

Consequently, initial and subsequent yield surfaces were probed in the first quadrant of stress space and strong

anisotropy was observed. This typical anisotropic mechanical behavior cannot be captured by only traditional

isotropic or kinematic hardening, or mixed hardening. Therefore, distortional hardening (i.e., distortional shape

evolution of yield surface) was proposed to characterize this anisotropic behavior during plastic deformation

based on internal state variables (ISV). It is found that the anisotropy of AZ31 extrusion bar can be captured by

constitutive models developed based on ISV and this constitutive model with Mandel stress is thermodynamically

consistent at finite deformation.

magnesium alloy, non-proportional loading, anisotropy, distortional hardening, internal state variables

F-50

Oxidation behavior of Mg-3.5Gd alloy by addtion of Ce and the internal oxidation mechanism at high

temperatures

Xiaowen Yu1, Bin Jiang1,2, Bo Liu3, Fusheng Pan1,2

1. State Key Laboratory of Mechanical Transmissions, College of Materials Science and Engineering, Chongqing

University, Chongqing 400044, China

2. Chongqing Academy of Science and Technology, Chongqing 401123, China

3. Chongqing Chang-an Automobile Co., Ltd, Chongqing 400023, China

The oxidation behavior of Mg-3.5Gd-xCe (x=0, 0.2, 0.4, 0.7 and 1.0 wt. %) alloys was investigated between

550 °C and 650 °C in the dry air. Micro-addition of Ce is effective in improving the oxidation resistance of

Mg-3.5Gd alloy. Mg-3.5Gd-0.2Ce and Mg-3.5Gd-0.4Ce alloys possess excellent oxidation resistance.

Morphologies and chemical compositions of the oxide films were analyzed. The oxide films of Mg-Gd-Ce alloys

mainly composed of MgO, Gd2O3 and a small amount of CeO2 according to X-ray diffraction (XRD) and X-ray

photoelectron spectroscopy (XPS). However, the oxidation resistance was deteriorated by further addition of Ce.

Severe internal oxidation was appeared in the sub-surface of Mg-3.5Gd-0.7Ce and Mg-3.5Gd-1Ce alloys after

oxidation at 500 °C for 6 h. The presence of Mg12Ce phases near the surface of the alloys caused the internal

oxidation.

Mg-3.5Gd, high temperature, Ce, Oxidation resistance, internal oxidation

F-51

The grain refinement effect of Sn3Y5 intermetallics in the as-extruded Mg-Sn-Y alloys

Ying Zeng1, Bin Jiang2, Gaofeng Quan1

1. Key Laboratory for Advanced Technologies of Materials, Ministry of Education, School of Material Science

and Engineering, Southwest Jiaotong University, Chengdu 610031, China

2. National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044,

28

China

The microstructures of the as-cast and as-extruded Mg-0.5Sn-xY alloys (x=0, 0.3; wt%) were observed to

investigate the effect of Y on the Mg-0.5Sn alloy. The results indicated that with the addition of 0.3 wt% Y to the

Mg-0.5Sn alloy, a tiny second phase dispersively distributed in the α-Mg matrix, which was confirmed as Sn3Y5

phase afterwards. Besides, the average grain size of the as-extruded Mg-0.5Sn alloys was refined by ~ 1/3 with Y

addition. On the other hand, the crystallographic orientation relationships (ORs) between Sn3Y5 and the matrix

were calculated by the edge-to-edge matching model, taking for the parameters for the phase field simulations of

the dynamic recrystallization (DRX). The ORs calculations results indicated that Sn3Y5 particles and matrix

showed small fr and fd values. Then, the phase field simulations described the grains nucleation and growing

during the whole DRX process, further confirmed that Mg-0.5Sn-0.3Y alloy with the Sn3Y5 particles performed

effective nucleation rate and Sn3Y5 could act as heterogeneous nucleation sites for α-Mg phase during extrusion

process.

Mg alloys; Grain refinement; intermetallics; Edge-to to-edge matching model; Phase field simulations

F-52

Research on Dynamic recrystallization of Mg-8Gd-3Y-1Nd-0.5Zr Alloy during Hot Deformation

Qi-Hongna1,2, Zhang-Zhimin1,2, Yu-Jianmin1,2, Yin-Xueyan1,2, Du-Zhiyuan1,2

1. Dept. of Material processing Engineering, North University of China, Taiyuan 030051, China

2. Engineering Technology Research Center for Integrated Precision Forming of Shanxi, Taiyuan 030051, China

Uniaxial hot compression was conducted on Gleeble-3500 thermo simulation machine.Based on stress-strain

curves, the constitutive relationship and the dynamic recrystallization kinetics model of Mg-8Gd-3Y-1Nd-0.5Zr

were established. Simultaneously, dynamic recrystallization mechanism of this alloy under different deformation

condition was investigated by SEM, EBSDand OM. The critical strain equation and the dynamic recrystallization

kinetics model were obtained. The results showed that the dynamic recrystallization volume fraction increased

with the increasing of the strain.The twin dynamic recrystallization(TDRX) was the mainly DRX mechanism at

350℃;the dynamiac recrysallization mechanism was dominated by continuous dynamic recrystallization(CDRX)

at 400℃ and 450℃ . At higher temperature(500℃ ), the dynamic recrystallization was dominated by

discontinuous dynamic recrystallization(DDRX) with a small amount of CDRX.

Keywords: Mg-8Gd-3Y-1Nd-0.5Zr alloy, dynamic recrystallization mechanism, work-hardening rate, kinetics

model

F-53

Improved ductility of high-pressure die-cast Mg-xCe-yAl-0.5Mn alloys by modifying Al/Ce ratio

Chuangye Su, Xiaoqin Zeng, Li Dejiang

Shanghai Jiao Tong University

Objective: Lightweight magnesium alloys have evoked an interest in the automotive industry for improving fuel

efciency through vehicle mass reduction in the past decade. Magnesium alloys are usually produced by

high-pressure die casting, which provides high productivity at a relatively low cost, especially for the manufacture

of complex, thin-walled, and near net shape parts. The high-pressure die-cast (HPDC) Mg alloys always show low

tensile ductility for containing a considerable amount of micro-porosity, which is hard to eliminate. Therefore,

other methods should be attempted to improve the ductility of the HPDC Mg alloys.

29

Methods: Alloys with nominal compositions Mg-xCe-yAl-0.5Mn (Al/Ce atomic ratio equals 0, 1.4, 2.1, 2.8, 3.7,

6.1, 8.7) were prepared by high pressure die casting machine (TOYO, BD-350V5). The alloy was melted and

injected into the mold at 973 K (700°C) with the temperature of the mold at 533 K (260°C). Secondary electrons

images were taken using an enhanced super resolution scanning electron microscopy (SEM, JEOL, JSM-7800F

Prime). The phase analyses were performed by the X-ray diffractometer (XRD, Rigaku Ultima IV) with Cu

K-alpha radiation. To acquire precise X-ray diffraction patterns, 10-100° 2θ range with 0.02° step was used.

Tensile specimens with a gage length of 50 mm and a gage diameter of 6.3 mm were tested at room temperature

using a Zwick-20 kN material testing machine with a strain speed of 3mm/min.

Results: The ductility and microstructure of high-pressure die-cast alloys Mg-xCe-yAl-0.5Mn (Al/Ce atomic ratio

equals 0, 1.4, 2.1, 2.8, 3.7, 6.1, 8.7) were investigated. The elongation of Mg-xCe-yAl-0.5Mn alloys increases

remarkably with the increasing Al/Ce atomic ratio, while tensile yield strength exhibits little change. The

elongation of the alloy with an Al/Ce atomic ratio of 3.7 reaches the maximum 14%, which improves 1300% than

that (1.0%) of the alloy with an Al/Ce atomic ratio of zero. Then the elongation decreases slightly when the Al/Ce

atomic ratio continues to increase. The improvement of the ductility results from the type and morphology of the

intermetallic compounds. For the microstructure of the alloy with an Al/Ce atomic ratio of zero, the alpha-Mg

matrix is surrounded by continuous network Mg12Ce intermetallics, which is incoherent with the alpha-Mg

matrix. The amount of Mg12Ce intermetallics decreases, while the amount of acicular Mg11Ce3 intermetallics

increases gradually with the increasing Al/Ce atomic ratio. The secondary phases in the alloy with an Al/Ce

atomic ratio of 3.7, are almost acicular Mg11Ce3 intermetallics with a diameter of 100nm and a length to diameter

ratio of over 10, which can pin the dislocations and block the grain boundary sliding effectively. Coarse and

isolated polygonal Mg17Al12 intermetallics form when the Al/Ce atomic ratio continues to increase, and cracks

are easily formed in the alpha-Mg/Mg17Al12 interface, therefore the elongation decreases slightly. It is concluded

that the alloy with an Al/Ce atomic ratio of 3.7, which approximates that of Al11Ce3 intermetallic, exhibits the

highest elongation.

Conclusion: It is concluded that the alloy with an Al/Ce atomic ratio of 3.7, which approximates that of Al11Ce3

intermetallic, exhibits the highest elongation.

ductility, die-cast, intermetallics

F-54

Experimental investigation and thermodynamic modeling of the Mg-Nd-Zr and Mg-Y-Zr systems

Kaiming Cheng1,2, Jixue Zhou1, Huoming Dong1, Lijun Zhang2, Yong Du2

1.Shandong Key Laboratory of High Strength Lightweight Metallic Materials, Advanced Materials Institute,

Shandong Academy of Sciences, Jinan, 250014, China

2. State Key Laboratory of Powder Metallurgy, Central South University, Changsha, 410083, China

Magnesium alloys attract great attention in recent years due to their low density and good castability. Among

various magnesium alloy systems, the participation strengthened magnesium-rare earth (Mg-RE-Zr) alloys exhibit

high operating temperature as well as improved creep resistance and strength. For instance, WE54 (Mg-1.5-2.0

wt.% Nd-0.4 wt.% Zr-1.5-2.0 wt.% heavy RE-5.0-5.5 wt. % Y) and WE43 (Mg-2.25 wt.% Nd-0.6 wt.% Zr-4 wt.%

Y) are successful commercial high temperature magnesium alloys. In this work, the equilibrium phase relations in

the Mg-Nd-Zr and Mg-Y-Zr systems are investigated in order to provide hints to the alloying composition

selection and the heat treatment process.

Phase relations in the isothermal sections of the Mg-Nd-Zr and Mg-Y-Zr systems at 500 °C are first investigated

through the diffusion couple technique and electron probe microanalysis (EPMA). Then, homogenous ternary

30

Mg-Nd-Zr and Mg-Y-Zr alloys are prepared in each ternary-phase regions and aged at 500 °C. The samples are

analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). No ternary compound is found in

the current systems. The solubility of Zr in the Mg-Nd and Mg-Y intermetallics is determined to be negligibly

little. Additionally, differential scanning calorimetry (DSC) are performed to construct the isopleth sections using

the aged alloys. Based on the present experimental results, CALPHAD-type assessment was performed to the

Mg-Nd-Zr and Mg-Y-Zr systems. Comprehensive comparisons between the calculated and measured phase

diagrams show that the present thermodynamic description could satisfactorily reproduce the experimental results.

The practical rules for selection of the additional RE elements and the heat treatment process of Mg-RE-Zr alloys

are discussed based on the present thermodynamic calculation.

Mg-Nd-Zr and Mg-Y-Zr systems; Diffusion couple; DSC; Phase diagram; Thermodynamic modeling

F-55

The role of Al content on deformation behavior and related texture evolution during hot rolling of

Mg-Al-Zn alloys

Fei Guo1,2, Dingfei Zhang1,2, Luyao Jiang1,2, Fusheng Pan2,3

1. College of Materials Science and Engineering, Chongqing University, Chongqing 400045, China;

2. National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044,

China

3. Chongqing Academy of Science and Technology, Chongqing 401123, China

Effect of Al addition on microstructure and texture evolution during hot rolling is investigated using Mg-(3, 6 and

9 wt.%)Al-Zn series alloys. X-ray diffraction technique is carried out for macrotexture measurement and electron

backscatter diffraction (EBSD) is used for the observation of microstructure and texture evolution during hot

rolling. The results shows deformation behavior, which includes twinning, dynamic recrystallization and

activation of slip system, are affected by the increase of Al content. Compared to AZ31 Mg alloys, the rolled

AZ91 sample exhibits strong basal texture in 20% rolling reduction and the intensity of basal texture decreases by

increasing rolling strain. Unlike double twins and contraction twins which are commonly observed in hot rolling

of AZ31 Mg alloys, twinning behavior is strongly suppressed by addition of Al content. The suppression of

twinning behavior hindered the formation of shear bands during hot rolling. It is observed some grain-like

extension twins nucleate inside unrecrystallized grains with ultrafine size in AZ91 which plays an important role

in texture evolution. The size of dynamic recrystallized grains in AZ91 is ultrafine compared to that of AZ31.

These recrystallized grains distribute along grain boundaries and would continuously coordinate further

deformation strain after their nucleation. The increase of area fraction of recrystallized grains results in a texture

weakness during large strain rolling in AZ91. Geometrically necessary dislocation information is analyzed for the

rolled samples. It shows prismatic slip takes an advantage in AZ31 rather than AZ91 during hot rolling, which

results in weaker basal texture for unrecrystallized grains.

Magnesium alloys; Microstructure; Texture; Dynamic recrystallization; Twinning;

F-56

Effect of yttrium and pre-treatments on the elevated temperature plastic behavior of as-cast AZ80

magnesium alloys

Lingbao Ren1,2, Gaofeng Quan1,2, Mingyang Zhou1,2, Wei Liang1,2, Qi Tang1,2, Dongdi Yin1,2

1. Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Sichuan, Chengdu, 610031, PR

China

31

2. School of Material Science and Engineering, Southwest Jiaotong University, Sichuan, Chengdu, 610031, PR

China

The plastic behavior and instability of as-cast AZ80 and AZ80M (AZ80+0.4Y wt.%) magnesium alloys were

studied by compression test at 573 K~673 K and at a strain rate of 10-4 s-1~10-2 s-1. There were three

pre-treatments for compression samples: as-cast (F), solutionizing (T4, 693 K×6 h, water quenching) and aging

(T6, 693 K×6 h, water quenching, 443 K×24 h ). T4 treatment could increase the peak stress from 105 MPa (F

state) to 150 MPa for AZ80, and 145 MPa (F state) to 165 MPa for AZ80M at 573 K, 10-2 s-1. The apparent

activation energy (Q) and stress exponent (n) of AZ80 and AZ80M in the state of F were calculated by the

hyperbolic sine constitutive model, respectively, in which the QAZ80=122 kJ/mol, QAZ80M=182 kJ/mol,

nAZ80=3.0, nAZ80M-=6.2. In the low temperature and high strain rate (573 K, 10-2 s-1) many intercrystalline

fractures were observed with obvious intercrystalline sliding trace. Intercrystalline fracture model with the

dynamic recrystallization (DRX) maintained the damage process when the temperature was high or the strain rate

was low. The processing map was established based on the compression plastic behavior using dynamic materials

model. Damage or unstable regions were demonstrated from micro to macro with optical microstructure analysis

and stress and strain distribution calculated by the finite element method (FEM). Moreover, the friction factor

between the samples and the compression die was taken into consideration to analysis its influence on the stress

distribution and damage process at elevated temperature.

AZ80 alloys; yttrium; constitutive model; processing map; friction factor

F-57

Effects of mish-metal on microstructures and properties of an as-extruded Mg-9Y-0.6Zr alloy

Bibo Li1,2, Kui Zhang1, Kaikun Wang2, Xinggang Li1, Yongjun Li1, Minglong Ma1, Guoliang Shi1, Jiawei Yuan1

1. State Key Lab for Fabrication＆Processing of Non-Ferrous Metals, Beijing Genera Research Institute for

Non-Ferrous Metals, Beijing, 100088, China

2. School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing, 100083,

China

The effects of 0%, 0.5%, 2% and 3.5% mish-metal additions on the microstructure and properties of an

as-extruded Mg-9Y-0.6Zr (WK90) alloy were investigated by optical microscope, X-Ray diffraction (XRD),

scanning electron microscope (SEM) and mechanical tester. The results show that the structure of as-extruded

WK90 alloy is composed of α-Mg matrix and extrusion streamline. After adding mish-metal, there generate

mish-metal phases (Mg3MM phase and Mg12MM phase). Moreover, with the increase of mish-metal addition,

the kinds and quantity of mish-metal phase increase, and the grain size of alloy gradually decrease. Both alloy

element Y and mish-metal would cause lattice expansion of magnesium matrix. Lattice constants of α-Mg phase

in Mg-9Y-3.5MM-0.6Zr, Mg-9Y-0.6Zr, Mg-9Y-2MM-0.6Zr, Mg-9Y-0.5MM-0.6Zr and pure Mg decrease

progressively. The addition of mish-metal elements can improve the alloy strength, and with the increase of

mish-metal content, the fracture strength of alloy increases first and then decreases, but the elongation always

declines. When the mish-metal content is 2%, the alloy has the highest ultimate tensile strength. The fracture

appearance showed that the fracture model of the as-extruded alloy is dominated as ductile fracture, and some

twins is observed. Twins decrease progressively until disappear with the increase of mish-metal content.

Furthermore, this study also finds that not only grain size but also the quantity, distribution and the morphology of

the second phase affect the alloy strength.

magnesium alloys; mish-metal additions; microstructure; lattice distortion; mechanical properties

32

F-58

Microstructure evolution and mechanical properties of Mg-10Gd-2Er-0.5Zn-0.6Zr alloy

Nannan Li, Zhaohui Wang, Xian Du, Ke Liu, Shubo Li, Wenbo Du

Beijing University of Technology

In the present work, the Mg-10Gd-2Er-0.5Zn-0.6Zr alloy was prepared with the procedure of permanent casting,

solid solution treatment, hot extrusion and aging treatment. The microstructure evolution and mechanical

properties of the alloy were investigated by Optical Microscope (OM), X-ray Diffraction (XRD), Scanning

Electron Microscope (SEM) and Transmission Electron Microscope (TEM). The mechanical properties of the

alloy were characterized by Vicker hardness and tensile tests at room temperature. The block and lamellar long

period stacking ordered (LPSO) structure can be obtained during the solid solution treatment. The existence of

LPSO structure can refine the grain size of extruded alloy when the dynamic recrystallization (DRX) occurred to

the Mg matrix. The peak-aged alloy exhibited tensile yield strength of 360MPa, ultimate tensile strength of 410

MPa and the elongation of 5%. The good performance of the alloy mainly results from the dense precipitation of

14H-LPSO structure and β, phase in the matrix during the solid solution and aging treatment. Besides, the LPSO

structures were kinked during the extrusion process, which can transfer the load from matrix and enhance the

elongation of the alloy.

Mg-Gd-Er-Zn alloy, LPSO, Microstructure evolution, Mechanical properties

F-59

Semi-solid Microstructure Formation Mechanism of AZ91D Magnesium Alloy

Hongyu Xu1, Ye Wang1, Zhao Yang1, Zesheng Ji1, Maoliang Hu1, Sumio Sugiyama2,1

1. School of Material Science and Engineering, Harbin University of Science and Technology, Harbin 150040,

China

2. Institute of Industrial Science, the University of Tokyo, 153-8505, Japan

In this paper, chip recycled pressing process (CRP for short), a new method for recycling magnesium alloy chips,

was put forward to prepare semi-solid billet. Semi-solid microstructure evolution and formation mechanism of

AZ91D original casting billet, extruded billet and CRP billet were studied. The spheroidizing mechanism and

coarsening mechanism of solid particle were analyzed. The formation process of spherical α-Mg solid particle

mainly included three stages, i.e., refining, spheroidizing and coarsening. During semi-solid isothermal treatment,

the equilibrium melting temperature drop and chemical potential drop caused by interfacial tension and interfacial

curvature were the fundamental cause of the spheroidizing and coarsening of solid particle. The coarsening of

solid particle was by means of Ostwald riping and merging growth. In fact, semi-solid microstructural evolution is

the course of atom diffusion.

CRP process, semi-solid microstructure, formation mechanism, spheroidizing mechanism, coarsening mechanism.

F-60

Influence of Pulsed Electric Current on the As-Rolled Microstructure and Rollability of Mg-3Al-1Zn Alloy

Jie Kuang1,2,3, Xiaohui Li3, Ruikun Zhang 1,3, Alan A. Luo2, Guoyi Tanga4

1. Key Laboratory for Advanced Materials of Ministry of Education, School of Materials Science and Engineering,

Tsinghua University, Beijing, 100084, PR China

2. Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43210, USA

33

3. Guangdong Institute of Materials and Processing, Guangdong Academy of Sciences, Guangzhou, 510650, PR

China

4. Advanced Materials Institute, Graduate School at Shenzhen, Tsinghua University, Shenzhen, 518055, PR China

Both electroplastic rolling (ER) and conventional warm rolling (WR) were conducted on AZ31 sheets. The

as-rolled microstructure and the rollability of the alloy under these two different processing routes were compared.

The pulsed electric current was found to promote the activation of contraction twins and lead to more

homogeneous plastic deformation, which results in the superior rollability of the alloy during ER.

F-61

Ultrahigh strength as-extruded Mg–10.3Zn–6.4Y–0.4Zr–0.5Ca alloy containing W phase

Jiang Hansi1, Xiaoguang Qiao1, Chao Xu2, Mingyi Zheng1, Kun Wu1, Shigeharu Kamado2

1. School of Materials Science and Engineering,Harbin Institute of Technology

2. Department of Mechanical Engineering,Nagaoka University of Technology

A new ultrahigh-strength W phase (Mg3Y2Zn3) containing Mg–10.3Zn–6.4Y–0.4Zr–0.5Ca (wt.%) alloy with

medium RE content has been fabricated through conventional casting and indirect extrusion. The as-extruded

alloy exhibits ultimate tensile strength of 466 MPa, tensile yield stress of 447 MPa and elongation to failure of

4.7%. The as-cast Mg–10.3Zn–6.4Y–0.4Zr–0.5Ca (wt.%) alloy is mainly composed of α-Mg and lamellar eutectic

α-Mg and W phase distributed at grain boundaries. After extrusion, the coarse lamellar W phases in the as-cast

alloy are broken into fine particles of about 0.5 μm, dispersing in the particle bands along the extrusion direction.

The as-extruded alloy exhibits a bimodal microstructure consisting of ultrafine dynamic recrystallized (DRXed)

grains with fine broken W phase particles at the DRXed grain boundaries and coarse un-DRXed regions. Large

number of nano W phase and small amount of nano β2′ phase are dynamically precipitated in the coarse

unDRXed regions during extrusion, which contribute to the ultrahigh strength of the as-extruded alloy.

Mg alloy; Extrusion; W phase; Precipitates; Mechanical properties

F-62

High cycle fatigue behavior and microstructure evolution in Mg-6Zn-1Mn alloy

Dingfei Zhang1,2, Daliang Yu1,2, Fusheng Pan2,3

1. College of Materials Science and Engineering, Chongqing University

2. National Engineering Research Center for Magnesium Alloys, Chongqing University

3. Chongqing Academy of Science and Technology

High cycle fatigue behavior of extruded and double-aged Mg-6Zn-1Mn alloy was investigated by servo-hydraulic

fatigue test frame under zero-tension load or full reverse tension-compression load. Post-fatigued specimens were

also studied by optical microstructures and EBSD. Results show that all the two alloys show more outstanding

high cycle fatigue performances in zero-tension load than that in tension-compression load. Double-aged alloy has

the highest fatigue strength in ZT load and the most deteriorative fatigue strength in TC load. Twinning and

detwinning mechanisms play a dominate role in fatigue deformation process in double-aged alloy. For extruded

alloy, in low stress cycles (cyclic stress ≤125 MPa) high cycle fatigue tests make a contribution to room

temperature recrystallization in Mg-6Zn-1Mn alloy. The grain refinement increased with increasing cycles. EBSD

analyses showed that dynamic recrystallization (DRX) has occurred in post-fatigued alloys, accompanied by the

presence of a high number density of low-angle grain boundaries (LAGBs). With the cyclic number increasing the

34

texture intensity was significantly weakened. The DRX in post-fatigued specimens was related to Continuous

DRX (CDRX) mechanism.

Magnesium alloy, High cycle fatigue, Twinning, DRX

F-63

Ageing behavior of Mg-8.2Gd-3.8Y-1Zn-0.4Zr alloy processed by high pressure torsion (HPT)

Wanting Sun1, Mingyi Zheng1, Xiaoguang Qiao1, Nong Gao2, Marco J. Starink2, Chao Xu3, Shigeharu Kamado3

1. Harbin Institute of Technology

2. University of Southampton

3. Nagaoka University of Technology

Objective：Homogenized Mg-8.2Gd-3.8Y-1Zn-0.4Zr alloy was HPT processed at room temperature, ageing

behavior of the HPT processed alloy at different temperatures were investigated, in order to clarify the influence

of HPT on ageingbehavior of the ultrahigh strength Mg alloy.

Methods: The direct-chill cast Mg-8.2Gd-3.8Y-1Zn-0.4Zr (wt%) alloy was homogenized at 510 oC for 12 h,

followed by immediate quenching into warm water at ~ 60 oC, and then was machined into the disks with a

diameter of 10.0 mm and a thickness of 1 mm. After ground with abrasive papers on both sides to final thickness

of ~ 0.85 mm, the disks were subjected to HPT processing with 10 turns at room temperature under imposed

pressure of 6.0 GPa and a rotational speed of 1 rpm. HPT-processed disks were aged at 90 oC, 120 oC, 150 oC

and 200 oC, respectively, for different periods followed by quenching in cold water.

Results: ageing precipitation behavior of the nano-structured Mg-Gd-Y-Zn-Zr alloy processed by HPT is

significantly different from that of the alloy processed by conventional extrusion / rolling processing. The

nano-structured sample aged at 120 oC for 12 h possessed a peak hardness of ~145 HV, which is much higher than

the peak-ageing hardness of the extruded sample. The segregations / clusters of solute atoms formed at dislocation

sites or / and grain boundaries contributed to the ageing hardening of the HPT processed Mg alloy. Moreover, the

average grain size is still remained around ~50 nm, which can be ascribed to such segregations / clusters act as

obstacles to grain growth and stabilize the nanostructure. The sample aged at 200 oC for 3 h exhibited a slightly

lower peak hardness than that aged at 120 oC, the main strengthening structure was still segregations / clusters of

solutes, while after ageing at 200 oC for 6 h (over-ageing), fine beta precipitates equilibrium phases were formed

at grain boundaries, which led to the hardness decrease.

Conclusion:Mg-Gd-Y-Zn-Zr processed by HPT contains a high density of dislocations and numerous grain

boundaries. The ageing behavior of the nano-structured alloy exhibits a unique ageing response as compared to

the conventional thermal deformed Mg-Gd-Y-Zn-Zr alloy. The peak ageing hardness of the alloy processed by

HPT is much higher than that of the alloy processed by conventional extrusion / rolling processing. The main

strengthening structure of the peak-aged Mg-Gd-Y-Zn-Zr processed by HPT was segregations / clusters of solute

atoms, rather thanmetastablephase precipitated in the peak-aged alloy processed by extrusion / rolling.

High pressure torsion; Mg-RE alloy; Ageing behavior; Grain boundary segregations; nano precipitates

F-64

Effect of Ca/Al ratio on microstructure and mechanical properties of Mg-Al-Ca-Mn alloys

Zitong Li1, Xiaodong Zhang1, Mingyi Zheng1, Xiaoguang Qiao1, Kun Wu1, Chao Xu2, Shigeharu Kamado2

1. School of Materials Science and Engineering, Harbin Institute of Technology

2. Department of Mechanical Engineering, Nagaoka University of Technology

35

Objective: Mg-Al-Ca-Mn alloys with Ca/Al mass ratios from 0.25 to 1.30 were cast and extruded. The total

amount of Ca and Al content was kept at about 6 wt.%. The effect of Ca/Al ratio on microstructure, texture and

mechanical properties of the Mg-Al-Ca-Mn alloys were investigated.

Methods: In the present study, Mg-4.4Al-1.1Ca-0.4Mn (wt.%), Mg-4.0Al-2.0Ca-0.4Mn (wt.%),

Mg-3.0Al-2.7Ca-0.4Mn (wt.%) and Mg-2.7Al-3.5Ca-0.4Mn (wt.%) alloys were fabricated by permanent mould

casting and extruded at 350℃ with an extrusion ratio of 12 and a ram speed of ~13 mm/s. The microstructure of

the as-cast and as-extruded Mg-Al-Ca-Mn alloys were observed by OM, SEM and TEM. The texture of the

as-extruded samples was measured by EBSD.

Results: The as-cast Mg-Al-Ca-Mn alloys with Ca/Al mass ratio less than 0.50 contain divorced and lamellar

eutectic (Mg,Al)2Ca. When Ca/Al ratio is greater than 0.90, fine lamellar Mg2Ca phase is formed in the as-cast

Mg-Al-Ca-Mn alloys. After extrusion, the second phases are broken and dispersed along the extrusion direction.

The area fraction of DRXed regions decrease with increasing Ca/Al ratio, the microstructure changes from an

almost fully recrystallized structure to a bimodal structure consisting of fine dynamically recrystallized (DRXed)

grains and coarse deformed regions. With increasing Ca/Al ratio, the DRXed grains and dispersed second phases

are refined. The as-extruded alloys exhibited a strong basal fiber texture, the intensity of which is increased with

increasing Ca/Al ratio. With increasing Ca/Al ratio, the {0002} texture component in the DRXed regions is

suppressed, and shifted to a {0002} texture component. The strength of the as-extruded Mg-Al-Ca-Mn alloys

increases significantly with increasing Ca/Al ratio. The as-extruded Mg-2.7Al-3.5Ca-0.4Mn (wt.%) alloy exhibits

a tensile proof strength of 438 MPa ultimate tensile strength of 457 MPa. The extraordinary high strength is

attributed to the ultrafine DRXed grains pinned by fragmented secondary phases, strong basal texture and dense

nano-scale precipitates.

Conclusion: The categories of second phase of the as-casted alloys are determined by the Ca/Al ratio. After

extrusion, with increasing Ca/Al ratio, the DRXed grains and dispersed second phases are greatly refined, thus the

strength of the as-extruded Mg-Al-Ca-Mn alloys increases significantly. Mg-Al-Ca-Mn alloys may have the

potential as next generation low-cost ultrahigh-strength alloys without RE elements.

Mg-Al-Ca-Mn alloys; Extrusion; Microstructure; Texture; Mechanical properties.

F-65

Application and Development of Gadolinium and Yttrium in Heat Resistant Magnesium Alloy

Nana Wang1,2, Jixue Zhou1,2, Lin Yuan3,

1. Shandong Key Laboratory for High Strength Lightweight Metallic Materials,Advanced Materials

Institute,Shandong Academy of Sciences,Jinan 250014,China

2. Shandong Engineering Research Center for Lightweight Automobiles Magnesium Alloys,Advanced Materials

Institute,Shandong Academy of Sciences,Jinan 250014 China

3. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 15000

Studies show that adding rare earth elements in to magnesium can significantly increase the comprehensive

mechanical properties of magnesium alloy,and have been widely used in the field of

aerospace ,military ,electronic products and so on. But it is not very sufficient about the effect of different rare

earth elements on magnesium alloys as well as microstructure mechanical action research, so in this paper

presented the characteristics of the rare earth elements Gd and Y,This paper reviews the applications and

developments of rare earth elements Gd and Y in heat resistant magnesium. Discussed the rare earth elements Gd

and Y in improving the heat resistant mechanism of magnesium alloy and the mechanism of magnesium alloy

strength.In addition analysised the problems of the current rare earth elements Gd and Y in the rearch of

36

magnesium. further development of Gd and Y in heat resistant magnesium was prospected,hoping to provide

reference to the research of new heat resistent magnesium alloy materials.

Gd;Y; Heat resistant magnesium;Microstructure

F-66

Assessments of Mg-containing ternary systems within the multicomponent magnesium alloy database,

TCMG4

Hai-Lin Chen, Shan Jin, Qing Chen, Johan Bratberg

Thermo-Calc Software AB

The multicomponent magnesium alloy thermodynamic database, TCMG4, has been developed for a wide range of

magnesium alloys of industrial relevance, including the Mg-Al based alloys such as AZ, AE, AJ, AM, AS and AX,

Mg-Zn-Zr alloys such as ZK60, Mg-RE (rare earth)-Zn (EZ) alloys and Mg-RE-Zr alloys such as WE and so on.

The database is developed in a 24-element framework

(Mg-Ag-Al-Ca-Ce-Cu-Fe-Gd-K-La-Li-Mn-Na-Nd-Ni-Pr-Sc-Si-Sn-Sr-Th-Y-Zn-Zr) and aimed to predict phase

equilibria and phase formation for Mg-based alloys. All relevant binary and ternary systems have been critically

reviewed. Reliable thermodynamic descriptions available in the literature were incorporated into the database with

necessary modifications to eliminate any inconsistencies. Many systems were reassessed in order to have most

up-to-date reliable and consistent thermodynamic descriptions. In such cases, the as-published experimental

results (especially as-cast microstructures) are systematically reanalyzed, in order to infer the hidden information

(such as primary phases during solidifications, phase formation sequences, microstructure features, phase

transformations and phase stability temperature ranges) that the investigators might have overlooked. For systems

that lacked both experimental data and thermodynamic descriptions, key experiments and first-principle

calculations were conducted to obtain necessary phase equilibrium data and thermodynamic data, which were then

utilized to perform thermodynamic assessments of these systems for the first time. With this new magnesium alloy

database, phase diagrams and liquidus projections of most important quaternary systems, which contains the main

components of some industrial magnesium alloys, have been calculated to investigate the phase equilibria in these

alloy systems. In this presentation, we report our recent progresses on the Ce-La-Mg, Ce-Nd-Mg, La-Nd-Mg,

Ca-Gd-Mg, Ca-Mg-Nd, Cu-Mg-Y and Cu-Li-Mg systems.

Mg-containing, multicomponent

Poster

F-P01

Effect of trace element Hf on precipitation process and recrystallization resistance in Al-Er-Zr alloys

Tonghui Liu, Shengping Wen, Yong Liu, Erqing Zhang

Beijing University of Technology

Abstract. Vickers hardness, electric conductivity and micro-structure analysis were used to study the effects of

trace element Hf atoms on precipitation and recrystallization resistance in Al-Er-Zr alloys. The results indicate that

the maximum values of Vickers hardness in Al-0.04Er-0.08Zr and Al-0.04Er-0.08Zr-0.05Hf (at. %) alloys are 56.2

HV, 58.9HV respectively, when ageing at 350 °C for 72h. The present research shows that the higher hardness

obtained in Al-0.04Er-0.08Zr-0.05Hf (at.%) mainly due to the formation of nanoscale and coherent Al3(Er, Zr, Hf)

37

precipitates, where the Al3(Er, Zr) praticals (LI2-structure) are detected in ternary alloy. Besides, a small number

of Hf atoms could decrease the condutivity of the quaternary alloy obviously. The recrystallization behavior of

two alloys which stay in peak ageing state was also studied. It shows that the recrystallization resistance of

Al-Er-Zr(Hf) alloys is slightly different, and the temperature is about 450 °C. The thermo-stability of

microstructure in ternary alloy is higher than the other one.

Al-Er-Zr alloy, Al-Er-Zr-Hf alloy, isothermal ageing, precipitation, recrystallization temperature

F-P02

Dry sliding wear of the microalloying Al-10Sn-4Si-1Cu alloy with Er and Zr

Jiuyan Liang, Xiaolan Wu, Wei Wang, Shengping Wen, Kunyuan Gao, Hui Huang, Zuoren Nie

Beijing University of Technology

A new composition of Al-Sn bearing material, Al-10Sn-4Si-1Cu-0.3Er-0.25Zr (all in wt.%), was designed in this

study. Meanwhile, the Al-10Sn-4Si-1Cu alloy was prepared for comparison. Two different heat-treatments, 375℃

for 100h and 300℃ for 4h, were conducted on the two alloys, and then the two alloys were cold rolled until the

deformations of them were 50%. Subsequently, an annealing at 300℃ for 4h were performed before they had

been cold rolled further to the thickness of 2mm. The dry sliding wear test was carried out under the load of 30N,

50N and 70N, respectively. The worn surfaces and the debris were characterized using SEM and EDS. The results

show that the hardness of the Al-10Sn-4Si-1Cu-0.3Er-0.25Zr alloy is 9% higher than that of the Al-10Sn-4Si-1Cu

alloy (about 67HV). Compared with the Al-10Sn-4Si-1Cu alloy, the mass loss of the

Al-10Sn-4Si-1Cu-0.3Er-0.25Zr alloy is 29% less and the worn surface is smoother, which means a better wear

resistant. The microalloying with Er and Zr can enhance the wear performance of the Al-10Sn-4Si-1Cu alloy.

Moreover , the wear mechanism of the two alloys will also be investigated in this paper.

Al-Sn alloy, microalloying, dry sliding wear, wear mechanism

F-P03

Hot deformation behavior and processing map of aluminum alloy 5E61

Ya Liu, Hui Huang, Ran Liu, Shengping Wen, Xiaolan Wu, Kunyuan Gao, Zuoren Nie

Beijing University of Technology

The hot deformation behavior of aluminum alloy 5E61 was studied by hot compressive tests using a Gleeble-1500

thermal simulator. The tests were performed at temperatures varying from 250-500℃ and strain rate ranging from

0.001-10s-1. The experimental data show the steady flow stress increases with decreasing temperature and

increasing strain rate, which can be represented by the Zener-Hollomon parameter. The related microstructure are

sensitive to deformation temperature ,strain rate and strain. The constitutive equation based on true stress- true

strain curves has been developed by hyperbolic sine equation with the hot deformation activation energy of

153.907KJ/mol. The softening mechanism is dominantly dynamic recovery .According to the TEM evolution, it

can be observed that Al3(Er,Zr) particles have precipitated in the aluminum matrix and some pin the dislocations,

which can effectively inhibit the dynamic recrystallization. Based on dynamic material model and Prasad’

instability criterion, the processing maps at strain of 0.3 and 0.65 have been established. Stable deformation

mainly occurs at high temperature with low strain rate. The processing map at strain of 0.65 exhibits two optimum

processing regions: one is at the temperature of 340 - 420℃ and strain rate of 0.001-0.003s-1; another is at

temperature of 420 - 480 ℃ and strain rate of 0.001- 0.01s-1

5E61 alloy, Hot deformation behavior, Constitutive equation , Processing map

38

F-P04

Microstructure, mechanical and corrosion properties of 5E61 alloy

Peiliang Liu, Xiaolan Wu, Shengping Wen, Hui Huang, Kunyuan Gao, Zuoren Nie

School of Materials Science and Engineering, Beijing University of Technology,Beijing 100124,China

Abstract: In this study, the microstructure of Al-6Mg-0.9Mn-0.07Zr-0.2Er (wt.%), registered as 5E61 alloy, were

investigated using optical microscopy, scanning electron microscopy and transmission electron microscopy. The

results show that the addition of 0.2 wt.% Er can refine the dendritic structure and form fine and coherent L12

structured Al3(ErxZr1-x) precipitates in the alloy. After a two-stage homogenization (280℃/10h, 460℃/36h), the

yield strength of 5E61 alloy is 376 MPa and the tensile strength is 452 MPa. The recrystallization temperature of

the alloy with 0.2 wt.% Er is about 15℃ higher than that of the alloy without Er. The better recrystallization

resistant may be related to the Al3(ErxZr1-x) precipitates, which can pin on dislocations and sub-grain boundaries.

The exfoliation corrosion and nitric acid mass loss test were also performed. The exfoliation corrosion of the alloy

is PA grade, and the mass loss is only 5.35mg/cm2.

5E61; Microstructure; Mechanical properties; Corrosion

F-P05

The effect of pre-aging temperature on the mechanical properties and corrosion behavior of a new type

Al-Zn-Mg-Cu-Er-Zr alloy

Juntai Lu, Hui Huang, Hao Wu, Shengping Wen, Kunyuan Gao, Zuoren Nie

School of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China

During the RRA treatment process, the effect of various pre-aging temperatures on the mechanical properties and

corrosion behavior of a new type Al-Zn-Mg-Cu-Er-Zr alloy was investigated by hardness tests, tensile property

tests, exfoliation corrosion tests (EXCO), intergranular corrosion tests (IGC), optical microscope (OM),

transmission electron microscopy (TEM). The results show that the corrosion resistance is not sensitive to the

pre-aging temperature, but the mechanical properties are sensitive. The retrogression time, when the hardness

reaches the valley value and apex value, is decreased during lower temperature pre-aging treatment. Whatever the

pre-aging temperature is 105℃ or 120℃, the RRA treated alloys possess a similar IGC and EXCO resistance

under the same retrogression time, but the alloys possess a better tensile property at the pre-aging temperature of

120℃. For the pre-aging treatment at 105℃ and 120℃, the grain boundary precipitates are discontinuity

distribution, but precipitates of the grain interior own a relatively smaller size and higher density after the 120℃

pre-aging treated.

Al-Zn-Mg-Cu-Er-Zr alloy, pre-aging temperature, mechanical properties, corrosion behavior

F-P06

Effect of the erbium content on the microstructure and mechanical property of 6061 aluminum alloy

wenjian Lv

Beijing University of Technology

The 6061 aluminum alloys with different contents of erbium were prepared in this paper. The erbium content was

optimized by grain refining effects and tensile strength. The solid solution treatment of the alloy with the best

erbium content was at the temperature ranged from 505℃ to 595℃ and the holding time of 4 hours. And then it

39

was aged at the temperature ranged from 160℃ to 200℃ and held 3 hours. It was showed that the grain size was

decreased with the addition of erbium, and it was the most effective when the erbium content was up to 0.15%.

Additionally, the tensile strength of as-cast alloy was 206Mpa to 243Mpa, which was up to 243Mpa at the erbium

content of 0.15%. The mechanical properties were consistent with the microstructures. Combined with the

microstructures and mechanical properties, the erbium content of 0.15% was the optimized content. It's heat

treatment was optimized to be aged at 180℃×3h followed by solid solution at 565℃×4h.

6061aluminum, erbium element, Mechanical Properties, Microstructure, Solution and aging treatment

F-P07

The effect of homogenization temperature on the microstructure and property of 6061 Aluminum alloy

with Erbium

Shasha Dong, Bolong Li, Wenjian Lv, Peng Qi, Zuoren Nie

Beijing University of Technology

The microstructure and mechanical properties of as-homogenized 6061 Aluminum alloy with 0.2wt% Er were

investigated. The microstructures of the as-casted and homogenized alloys were analyzed using Optical

microscopy (OM) and scanning electron microscopy (SEM). Energy dispersion X-ray spectroscopy (EDS) was

used to analysis the phase chemical composition. The properties analysis of alloy employed Vickers hardness. The

as-casted alloy has the hardness of 80.6HV. The results showed that the homogenizing treatment had a significant

influence on the precipitation morphology of the alloy. Rising with the homogenization temperature, the long

strip-liked Fe-rich grain distributed on the boundary phase

became discontinuous and sparseness, transforming to short rod and granular shape. The Mg2Si phase

disappeared along the grain boundary. In addition, the Fe-rich phase with a large fish-bone structure became

smaller. During homogenizing treatment, a large number of dispersed Mg2Si phase appeared inside grains, and

the number of phases containing Er were dissolved into the matrix in contrast. The hardness of homogenized alloy

was up to 77.9HV. In addition, the alloy optimal homogenization temperature was 570℃ according to the

experimental data.

Homogenization Temperature, Microstructure, Mechanical Properties, 6061 Aluminum Alloy with Erbium.

F-P08

Effects of electromagnetic stirring frequency on the microstructure and mechanical properties of

Al-7Si-0.42 Mg-0.1Cu alloy by semi-solid processing

Peng Qi, Bolong Li, Wenjian Lv, Tongbo Wang, Zuorean Nie

Beijing University of Technology

Semi-solid processing is one of the most promising technologies. Rather than liquid processing, the primary α-Al

particles of the semi-solid Al-Si alloys are refined, which are nearly spherical and uniformly distributed. This

paper studies the effect of the electromagnetic stirring frequency on the microstructures and mechanical properties

of semi-solid Al-7Si-0.42Mg-0.1Cu alloys. The samples were prepared by electromagnetic stirring at different

frequency after low temperature pouring. The effect of frequency on the microstructure and property was studied

by metallographic analysis, scanning electron microscopy and mechanical testing. The average equivalent circular

diameter was decreased from 127μm to 95μm until the stirring frequency was10 Hz. Meanwhile the average shape

factor was increased from 0.40 to 0.75. The dendritic α-Al particles were generated, and the grains grow up to

117μm at the frequency of 15 Hz. The tensile strength of alloys was increased from 193.02 MPa to 212.54 MPa

40

until the stirring frequency was 10 Hz, and the elongation increased to 6.67% from 3.73%. The fracture

morphology of the sample that was prepared by semi-solid processing at 10 Hz in frequency presented more

dimples. Therefore, the best electromagnetic stirring frequency was 10 Hz.

Electromagnetic stirring, semi-solid, microstructure, tensile properties, fracture

F-P09

Rapid solidification of ternary Al-Cu-Ag alloys under free fall condition

Fuping Dai, Wei Zhai, Bingbo Wei

Department of Applied Physics, Northwestern Polytechnical University, Xi'an 710072, China

Al-Cu-Ag eutectic type alloys are often widely used in industrial applications because of their good mechanical

properties. Also this system serves as a typical model for better understanding the solidification mechanism of

ternary eutectic alloys. Under the equilibrium solidification condition, the ternary Al-Cu-Ag eutectic alloys

involves the cooperative growth of three eutectic phase (Al), (Al2Cu) and (Ag2Al). However, the solidification

path and microstructure evolution of such alloys under high undercooling conditions exists some uncertain

problems and needs to be further explored. The temperature of eutectic transitions of ternary Al-Cu-Ag eutectic

alloy falls within medium temperature range is therefore suitable for space experiments. Using a drop tube

technology to simulate the space environments and to achieve high undercooling level is a effective technology to

explore the mechanism of rapid solidification of the ternary Al-Cu-Ag eutectic alloy.

In the present work, the rapid solidification of the ternary Al68.5Cu14.1Ag17.4 eutectic alloy and other three

ternary Al-Cu-Ag alloys in primary (Al), (Al2Cu) and (Ag2Al) phase areas around the ternary eutectic point is

realized by 3m ultrahigh vacuum drop tube facility. The samples were superheated about 200 K

with RF induction heating and atomized into small droplets with diameters of 100-800μm by exerting high

pressure Ar gas. The dispersed droplets are rapidly solidified into particles during free fall. Both the cooling rate

and undercooling versus droplet diameter of liquid alloys are theoretically calculated.

The maximum undercooling for ternary Al68.5Cu14.1Ag17.4 eutectic alloys is up to 235K (0.30 TE). Under the

lower undercooling condition, the microstructure is characterized by regular lamellar ternary (Al+Al2Cu+Ag2Al)

eutectics. Once the undercooling is higher than 109K, anomalous ternary (Al+Al2Cu+Ag2Al) eutectic cells are

formed, which show spherical shape and remarkably refines with undercooling increase. When the undercooling

of the droplet is up to 235K, the whole sample become one spherical anomalous ternary (Al+Al2Cu+Ag2Al)

eutectic cell. As for Al77.9Cu15Ag7.1 and Al75.1Cu18.4Ag6.5 alloys, the primary (Al) and (Ag2Al) phase both

develop into as snow-like equiaxed grains. With the increase of undercooling, pseudo-binary ( (Al+Ag2Al)

eutectic is formed in these two alloys. By contrast, the primary Ag2Al phase in Al63.9Cu15.5Ag20.6 alloy grows

through faceted way, and no binary eutectic structures can be found in this alloy. If the undercooling for

Al77.9Cu15Ag7.1, Al75.1Cu18.4Ag6.5 and Al63.9Cu15.5Ag20.6 alloys attains 125, 171 and 189 K respectively,

the microstructures only consist of tiny ternary (Al+Al2Cu+Ag2Al) eutectic colonies. It is shown that the

undercooling changes the solidification path of Al-Cu-Ag eutectic-type alloys by suppressing the formation of

primary phases and pseudo-binary eutectics and brings about remarkable refinement effect to ternary

(Al+Al2Cu+Ag2Al) eutectic structure.

drop tube, aluminum alloy, dendritic growth, eutectic growth, rapid solidification

F-P10

In situ observation Zr poisoning effect in Al alloys inoculated by Al-Ti-B

Yiwang JIA, Da SHU

41

Shanghai Key Laboratory of Advanced High-temperature Materials and Precision Forming, Shanghai Jiao Tong

University

It has been widely reported that the performance of Al-Ti-B refiners is dramatically worsened when using them in

aluminium alloys containing Zr , and the mechanism of Zr poisoning is not clearly understand. The solidification

of three Al-20Zn alloys containing different Zr contents (0, 0.1wt.% and 0.2wt.%) and holding at two different

temperatures (730℃ and 780℃) with different times was investigated in situ by synchrotron X-ray radiography

at the BL13W beamline of Shanghai Synchrotron Radiation Facility. The results show that the evolution of the

number of grains in solidification is well fitted by a logistic model. As the undercooling needed for nucleation is

expanded with the increasing of Zr contents, this means the nucleation potence of TiB2 particles is worsed. The

degree of poisoning effect is aggravated with the increasing of Zr contents, holding temperature and holding time.

Zr poisoning; Al alloys; solidification; X-ray radiography

F-P11

Superplastic Deformation Behavior of Fine Grained 1420 Al-Li Alloy with Pulsed Current

Yanling Zhang1,3, Hongliang Hou1,2,3, Jing Bi1

1. Beijing Aeronautical Manufacturing Technology Research Institute

2. Aeronautical Key Laboratory for Plastic Forming Technologies

3. Beijing Key Laboratory of digital plasticity forming technology and Equipment

The effects of pulsed current density, frequency and duration on superplastic deformation properties of 1420 Al-Li

alloy were investigated by uniaxial superplastic tensile tests under the assistance of pulsed

current, and the optimal electrical parameters were obtained. By conducting comparative experiments with or

without electropulse, influences of pulsed current on superplastic deformation properties and microstructure were

studied. The results showed that there was a threshold value of current density jc of 150A/mm2, when the current

density j exceeds jc the elongation was firstly increased and then decreased with current density j raised. When the

frequency and duration increased, the elongation was firstly increased and then decreased. The optimal electrical

parameters for superplastic deformation were 192A/mm2 of current density, 150Hz of frequency and 30s of

duration at 480℃ and 0.001s-1 , and under that condition, the elongation was raised by 68% compared to that

without electropulse. Furthermore, the grain was refined and the average grain size was reduced after superplastic

deformation with the optimal electropulse. It was noted that electropulse could not only improve the deformation

property and reduce the peak stress, but also promote the recrystallization and restrain the grain growth.

1420 Al-Li alloy, superplastic deformation behavior, electropulse, microstructure.

F-P12

Research on deformation characteristics of butterfly die extrusion process of aluminum profiles

Lei Cheng, Guojie Huang, Wei Xiao, Jianwei Wang

State Key Laboratory of Nonferrous Metals and Processes, General Research Institute for Nonferrous Metals,

Beijing 100088, China

The aluminum alloy profiles with high performance are very important structural material, widely used in industry

of aerospace, aviation, transportation and shipbuilding. The technology of extrusion die design and manufacture is

key point and bottleneck of production of high performance aluminum profiles. It is a challenging task for die

design and fabrication of high performance aluminum profiles, which has thinner wall, larger width, higher

42

accuracy dimension, complex cross-section shape. So, the traditional die design method based on experience and

“try-and-error” has not satisfied the requirement of modern industrial development. In addition, extrusion

production of aluminum profiles in process using traditional porthole die will inevitably bring irregularity of

material microstructure and properties, coarse grain ring and severe grain coarsening, which will result in the

lower comprehensive yield.

A new type aluminum extrusion die namely design technique of butterfly die was introduced. Designing a

butterfly die means giving the bridges an arched shape in place of the typical edged shape. The height in the

central part of bridge was lower. The shape of the bridges helps to reduce breakthrough pressure, and to improve

the flow behavior of aluminum during extrusion.

The main structures of butterfly die and its features were studied. Examples of butterfly dies practical implication

in aluminum alloy hollow profiles extrusion were listed. Metal flow and deformation behavior in butterfly die

extrusion process were studied systematically based on numerical simulation method. Effects of die structure

parameters, such as the sinking height of dividing bridge, the depth of second feeder and the radius of arched

bridge, on metal flow, extrusion load and die stress were investigated, and it was compared with the traditional die.

The simulation results show that when the aluminum profile is extruded using the butterfly die, the metal flow and

deformation are more homogeneous than those of the traditional die, and the dead metal zone at the top of

dividing bridge and welding chamber decreases. Furthermore, the extrusion load curve is smoother and there is no

obvious mutation change. The breaking portholes load and the maximum extrusion load of the butterfly die are

reduced by 72.2% and 17.3%, respectively. The effective stress distribution is more uniform, and the maximum

effective stress is reduced by 11.2%，which improves the die operating life. Moreover, the elastic deformation of

the dividing bridge is lowered, and the stability of the die core is improved.

Aluminum profiles in extrusion process using butterfly die can improve Microstructure and deformation

uniformity of metal, this is helpful to increase the welding quality of the welding seam. It can reduce extrusion

force and raises production efficiency at the same time. So, aluminum profiles using porthole die extrusion is a

kind of high-efficient production technology.

butterfly die; aluminium profiles; deformation characteristics; numerical simulation; extrusion

F-P13

Effect of cyclic pre-deformation on the tensile behavior of fcc metals with different stacking fault energies

Ming-Jie Niu1, Dong Han1, Ying Yan1, Meng Lu1, Feng Shi1, Xiao-Wu Li1,2

1. Department of Materials Physics and Chemistry, School of Materials Science and Engineering, Northeastern

University, Shenyang 110819, P.R. China

2. Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University,

Shenyang 110819, P.R. China

In the practical engineering applications, the mechanical properties of materials will become weakened with the

accumulation of fatigue damage. Therefore, more attention has been paid to the study on the cyclic

pre-deformation effect on the mechanical behavior of materials. However, a deep understanding of the

micro-mechanism of the fatigue pre-deformation effect on mechanical behavior of materials still remains lacking.

Therefore, in the present work, some typical fcc metals (like Al, Cu, Cu-Al alloys) with different stacking fault

energies (SFE) are selected as the target materials, and the effect of cyclic pre-deformation on their static

mechanical behaviors are systematically studied.

The uniaxial tensile yield strength obviously increases for commercially pure (CP) Al pre-fatigued at a stress

amplitude of 30 MPa (stress ratio R = -1) to different damage level D (= pre-cycle N/ fatigue life Nf) ranging from

43

2% to 75%, and the uniform strain is improved at the D being between 2% and 50%, meanwhile, higher ultimate

tensile strength is remained.

For pure Cu polycrystals, with increasing the total strain amplitude Det from 5.0 × 10-4 to 5.0 × 10-3, the

dislocation structures transform from veins into walls, labyrinth and loose cells, and further into walls and cells;

the cyclic stress increases and eventually all enters into a saturation stage. Compared to the unfatigued specimen,

after pure Cu is pre-deformed to the same accumulated plastic strain at different Det/2, the tensile strength

decreases slightly, whereas the yield strength somewhat increases, but the elongation decreases significantly at

lower total strain amplitudes Det/2 of 5.0 × 10-4 and 1.0 × 10-3 ;. as the Det/2 is as high as 5.0 × 10-3, the tensile

strength and the elongation just decrease slightly, whereas the yield strength is significantly improved.

Cu-16 at.% Al alloy undergoes a sustained cyclic hardening stage at different total strain amplitudes (1.0 ′ 10-3,

2.3 ′ 10-3 and 3.7 ′ 10-3), and no stress saturation phenomenon takes place. With increasing strain

amplitude, the cyclic stress increases evidently. Compared to the unfatigued specimen, the ultimate tensile

strength of the specimen pre-cycled at the lowest total strain amplitude of 1.0′10-3 is largely raised, at no

expense of tensile ductility. With increasing the total strain amplitude, the uniform strain and ultimate tensile

strength decreases, while the yield strength reaches the maximum value at the highest total strain amplitude of 3.7′

10-3.

In order to explore the micro-mechanism of fatigue pre-deformation effect on static mechanical properties of Al,

Cu and Cu-Al alloys, the corresponding surface deformation features and sub-structures are studied and analyzed

by SEM and TEM observations, respectively. Through the comparisons of the relevant experimental results

obtained with different SFE metals such as Al, Cu and Cu-16at.%Al alloy, it is found that a low-cycle fatigue

training treatment at an appropriate condition causes a better strengthening effect on the static tensile properties

for fcc metals, especially for low SFE metals.

Copper, Aluminum, Cu-Al alloy, fatigue pre-deformation, uniaxial tension, microstructure, stacking fault energy

F-P14

Effect of solution treatment on microstructure and mechanical properties of Al-Zn-Mg-Er-Zr alloy

Hao Wu

Beijing University of Technology

The effect of solution treatment on microstructure and mechanical properties of Al-Zn-Mg-Er-Zr alloy were

investigated by means of optical microscopy (OM), scanning electron microscope (SEM), scanning electron

microscopy (SEM), transmission electron microscopy (TEM), tensile test and hardness measurement. The volume

fraction of residual phases and the distribution of grain boundary precipitates were characterized. The results show

that the solution treatment had a significantly effect on microstructural and mechanical properties. With increasing

single-stage solution temperature or time, the residual phases are dissolved into Al matrix gradually, and the

number density of residual phases decreased. Thus, the strength of the single-stage solution treated samples

increase first and then decrease. Compared with the single-stage solution, the enhanced solution treatment can

improve the dissolution of residual phases, which can lead to a higher strength. The grain structure of the high

temperature pre-precipitation treated sample is similar as that of the enhanced solution treated sample, but owing

to the effect of pre-precipitation treated process, a mass of AlZnMgCu phase precipitating from the Al matrix and

the grain boundary precipitates are more discrete and coarser, resulting in a lower strength. Moreover, the effect of

the presence of L12-structured nanometer-sized Al3(Er,Zr) particles on the microstructural evolution during

solution treatment has also been discussed in detailed.

Al-Zn-Mg-Er-Zr alloy,Solution treatment, Microstructure, Mechanical properties, Al3(Er,Zr) particles

44

F-P15

Research on diffusion bonding of 1420 Al-Li alloys assisted by electro- magnetic force

Fan Wu1,2, Wenlong Zhou1, Yujie Han2, Tao Niu2, Hongliang Hou2

1. School of Material Science and Engineering,Dalian University of Technology.

2. Beijing Aeronautical Manufacturing Technology Research Institute.

The influence of the electro-magnetic force(EMF) on the basic mechanism of diffusion bonding is discussed in

this paper. The EMF produced by the discharge of the pulsed magnetic field was applied on the diffusion bonding

of 1420 Al-Li alloy sheets. The mechanical properties of the diffusion bonding joints were characterized by shear

strength, which were detected by universal testing machine(UTM). Then, the interface and shear fracture

microstructures were observed by optical microscope(OM) and scanning electron microscope(SEM), respectively.

The results show that, compared with the traditional diffusion bonding techniques, the EMF assisted diffusion

bonding can break the oxide layer, increase the interface sheets substrate contact area, and decrease the bonding

time significantly. The power of the pulsed magnetic field was discharged on a special uniform press coil to

generate the electro-magnetic force. The joint with the highest shear strength of 150 MPa was achieved in 1200

seconds under 520℃, 12kV and 10 times discharge cycles.

Al-Li alloys; Diffusion bonding; Pulsed magnetic field; Electro-magnetic force; Shear strength.

F-P16

Influence of Yb modification on the microstructure and mechanical propertyof an A356.2 aluminum alloy

shaochen zhang

University of Jinan

The A356.2 aluminum alloy (Al–7Si–0.35Mg) has been widely used in automotive and aircraft industries. But

coarse grains and thick needle shape eutectic Si in A356.2 lead to low mechanism properties. Previous studies

have found that rare earths can metamorphose A356.2 greatly which has long modification time and very stability.

The effect of Yb addition(0,0.2,0.4 and 0.6%wt.%) and T6 heat treatment on microstructures and mechanical

properties of A356.2 alloy have been investigated in this work. Microstructures of specimen after T6 treatment

were examined by optical microscope, scanning electronic microscope and mechanical properties were examined

by tensile testing machine and Brinell hardenss tester. Experimental results show that Yb not only can modify the

eutectic silicon, reduce the size of α-Al but also can changed the Si morphology from needle-like to fine

spheroidal particles. With the increase of Yb content, the ultimate tensile strength (UTS) increased gradually.

When adding 0.4%Yb, the ultimate tensile strength (252 MPa) and hardness (97.3HB) can be the highest. It is

increased by 10.12% and 37.66% combined with no Yb addition. When the amount exceeds 0.4%, eutectic silicon

could have edges and begin to coarse along with the UTS and hardness declining. The DSC curves of specimen

shows that Yb addition resulted in decreasing eutectic temperature which is beneficial to mechanical properties of

A356.2 alloy. Tensile fracture analysis showed that the mechanism of A356.2 aluminum alloy after T6 treatment

was transgranular/intergranular mixed mode of fracture. The fracture mode is brittle fracture and many rivers and

tear-shaped are seen on fracture section.

A356.2; Rare earth elements; Aging process; Metamorphic; Mechanical Property

F-P17

Study on the Microstructure of As-Cast 7085 Aluminum Alloy During Homogenization

45

Yuewen Shao, Yi Liu, Jinfeng Leng, Kun Zhu, Zemei Liu, Chenxue Li

Material Science and Engineering, University of Jinan

Objective:Investigate the effect of the two-stage homogenization on 7085 aluminum alloy.

Method:The microstructure of as-cast high strength 7085 aluminum alloy during two-stage homogenization was

studied by optical microscopy (OM), X-ray diffractometer(XRD), scanning election microscopy (SEM), energy

dispersive spectrometer(EDS) and differential scanning calorimeter(DSC).

Result:The severe dendritic segregation existed in as-cast 7085 aluminum alloy and a small amount of Al7Cu2Fe

existed in the as-cast 7085 alloy. Analysis of DSC indicated that the melting point of eutectic was 473.43℃, so the

homogenization temperature was determined below 473.43℃ . In two-stage homogenization scheme, the

specimens were homogenized at 200℃/12h+470℃/12h,400℃/12h+470℃/12h and 300℃/8h+465℃/24h.

Conclusion:The evolution of primary eutectic structure of 7085 alloy was found, which consists of three processes:

dissolution of non-equilibrium eutectic phase IFNa(Al)+ Mg(Zn)2, transformation from Mg(Zn)2 to Al2CuMg

and the dissolution of new phase Mg(Zn)2. A optimization two-stage homogenization scheme for as-cast 7085

aluminum alloy is 300℃/8h+465℃/24h.

7085 aluminum alloy; Microstructure; Homogenization annealing; Precipitated phase

F-P18

Effect of alloy composition on microstructure evolution and mechanical properties of AA6010 alloy

Jin Fu1,2, Xiaohui Li1, Wenjun Qi1, Yajiang Li2

1. Guangdong Institute of Materials and Processing, Guangdong Academy of Sciences, Guangzhou 510650, China

2. College of Materials Science and Engineering, Shandong University, Jinan250061, China

The effect of alloy compositions on microstructure evolution and mechanical properties of AA6010 alloys was

investigated with different mass fractions of copper ranged from 0.2% to 0.6%. The morphologies of particles

distributed in the alloy were analyzed through scanning electron microscope (SEM) equipped with energy

dispersive spectrometers (EDS) systems. The mechanical properties of the sheets in the hot extruded state,

including yield strength (YS), ultimate tensile strength (UTS) and elongation, were carried out on DNS200

machine. Hardness was measured on the MH-5L Vickers hardness tester. The results indicate that the as-cast

microstructure consists of crystalline phases of AlMgSi, AlMgSiCu and Al(Fe,Mn)Si. After hot extrusion, the

phase was broken and distributed along the extrusion direction, without chemical composition change. Proper

content of Cu element can refine the microstructure and enhance the strength. The average grain size was 6.5 μm,

5.8μm and 4.3 μm, respectively. Tensile test shows the strength increased and the elongation decreased followed

by increasing copper content, respectively. However, the yield strength, ultimate strength and elongation of alloy

with 0.2%Cu were 91MPa, 180 MPa and 30%; and alloy with 0.4%Cu were 105 MPa, 189 MPa and 27%; and

alloy with 0.6%Cu were 115 MPa, 205 MPa and 26%. Fracture morphology exhibited typical dimple fracture

pattern. Finally, the alloy has a higher strength and a good plastic deformability than without the Cu elements.

AA6010 alloys, microstructure evolution, mechanical properties, texture evolution.

F-P19

Investigation on TiN-Al composite coatings of A356 alloy by mechanical alloying

Zhengui Yuan, Luyao Pan, Shan Jiang, Min Zuo

University of Jinan

46

The TiN-Al composite coatings on A356 alloy were successfully synthesized by mechanical alloying (MA) of Al,

TiN and C powders under argon atmosphere. Meanwhile, the optimal parameters for mechanical milling

processing were determined by changing the material ratio (Al: TiN: C), milling time, the ball-to-powder weight

ratio, which might have a significant improvement on the wear resistance of A356 alloys. The microstructures and

mechanical properties of A356 alloy samples with TiN-Al composite coatings were characterized by means of

X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with energy dispersive X-ray

spectroscopy (EDS) and Brinell hardness test. It was worth noting that under the optimal conditions, i.e. the

material ratio of (Al: TiN: C= 17.5:1.5:1), the ball-to-powder weight ratio of 14:1 and the milling duration of 12 h,

the Brinell hardness of sample with TiN-Al composite coating could be remarkably increased to 143.80 HBW,

indicating the wear resistance of aluminum alloys could been significantly improved by TiN-Al composite coating

fabricated by MA process.

A356 alloy; TiN-Al composite coating; Mechanical alloying; Brinell hardness; Interface microstructure

F-P20

The effect of initial micro-structures on deformation behaviors of commercial pure titanium

Tongbo Wang, Bolong Li, Mian Li, Zuoren Nie

Beijing University of Technology

Abstract: In this paper, the effect of initial micro-structures on the deformation behaviors of commercial pure

titanium was elaborated by investigating the evolution of dislocation boundary and its adiabatic shear sensitivity.

The low-speed deformation was carried on the Gleeble-3500 simulator, and a higher-speed deformation was

realized by the split Hopkinson bar. The dislocation substructures were analyzed by transmission electron

microscope. At the low or medium strain rates, the main plastic deformation mechanism of as-annealed

commercial pure titanium was dislocation slipping. Meanwhile, geometrically necessary boundaries (GNBs) with

different directions were generated and crossed with each other. However, new dislocation boundaries were

formed in as-cold rolled plates, which were parallel to the initial ones induced by cold rolling. When the strain rate

was up to 1000 s-1, the initial dislocation boundary played an adverse role in the adiabatic shear sensitivity of

commercial pure titanium. The adiabatic shear band was the high-speed deformation characteristic micro-structure

in commercial pure titanium. In addition, dynamic recrystallized grains were generated in the center of the

adiabatic shear band, whose formation was consistent with the sub-grain rotation mechanism.

Dislocation boundary, Slipping, Adiabatic shear band

F-P21

Transmission electron microscopy investigation of twin boundary and shear band structures in dynamically

deformed gamma-TiAl intermetallic compound

Guang Yang1,2, Kui Du2, DongSheng Xu3, Yang Qi1, HengQiang Ye1,2

1. School of Materials Science and Engineering, Northeastern University, Shenyang 110819, People’s Republic of

China

2. Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of

Sciences, Shenyang 110016, People’s Republic of China

3. Division of Titanium Alloys, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016,

People’s Republic of China

Objective: TiAl intermetallic compounds are promising high temperature structural materials, which have

47

potential to substitute superalloys for low-pressure turbine blades. Considering the complex stress state

experienced by the turbine blades, it is necessary to study the dynamical deformation of gamma-TiAl intermetallic

compound.

Methods: A polysynthetic twinned (PST) Ti-49.5Al single crystal was used in this study. A cylinder of TiAl crystal

was grown in the crystallographic direction by using optical floating zone method. A bar was cut from the cylinder

and then deformed at a strain rate of 103s-1. Transmission electron microscopy (TEM) specimens were made

from the deformed sample. TEM observations were carried out on an FEI Tecnai F30 transmission electron

microscope and a Titan G2 60-300 aberration-corrected scanning transmission electron microscope.

Results: Deformation twins and shear bands were observed in the deformed sample. Primary twin lamellae are

slightly less than 100 nm in thickness. They have (11-1) twin plane with the matrix. Secondary twins are formed

inside the primary twin lamellae and they have a dimension of several to tens of nanometers. Steps are observed

on the twin boundaries (TBs) with high-resolution high-angle annular dark-field (HAADF) imaging. In addition,

shear bands are observed initiating from severe distorted twin boundaries. When the shear band propagated

through primary twin lamellae, they cause severe displacements of the twin lamellae across the shear band. When

several shear bands propagate in the same direction, a herring-bone structure occurs, which is composed of twin

lamellae inside and between these shear bands.

Conclusion: For the gamma-TiAl intermetallic compound in L10 ordered structure, deformed twins and shear

bands were observed after dynamic deformation. Detailed twin boundary structures were resolved by

aberration-corrected scanning transmission electron microscopy.

gamma-TiAl, dynamic deformation, twin, shear bands

F-P22

Hot deformation behavior and microstructural evolution characteristics of an as-extruded Ti-44Al-5V-1Cr

alloy containing the beta phase

Hongwu Liu1,2, Fan Gao2, Zhenxi Li2, Qingfeng Wang1

1. State Key Laboratory of Metastable Materials Science and Technology, Yanshan University

2. Titanium Alloys Laboratory, Beijing Institute of Aeronautical Materials

The hot deformation behavior and microstructural evolution of an as-extrudedTi-44Al-5V-1Cr alloy containing

the β phase were investigated by hot compression tests at temperatures of 900–1250°C and strain rates of

0.001–1s-1. It was indicated that the dependence of peak stress on deformation temperature and strain rate could

be accurately described by a hyperbolic sine type equation. The activation energy, Q, was estimated to be 452.17

kJ/mol. The hot processing map of the as-extruded Ti-44Al-5V-1Cr alloy was developed at a strain of 0.3 on the

basis of dynamic materials modeling and the Prasad criteria. There were four different domains in the hot

processing map, according to the efciency of power dissipation, η. The flow soft and hot deformation mechanisms

for different domains were illustrated in the context of microstructural evolution during the process of deformation.

As a result, the optimized windows of deformation temperature/rate for secondary hot processing of the

as-extruded Ti-44Al-5V-1Cr alloy were determined to be1125–1150°Cnear 0.001s-1 for superplastic forming. The

Ti-44Al-5V-1Cr alloy sheet was successfully manufactured at1250°C with a strain rate of 0.1–0.5s-1.

beta phase containing TiAl; Hot processing map; Dynamic recrystallization; Superplasticity

F-P23

Variant selection of {332} primary and secondary twinning in beta-type Ti-Mo alloy

Xueyin Zhou, Xiaohua Min, Congqian Cheng, Jie Zhao

48

School of Materials Science and Engineering, Dalian University of Technology, 116024, P.R.China

Tensile properties of solution-treated beta-titanium alloys depend strongly on their deformation mode. A typical

deformation mode for beta-titanium alloys is {332}<113> twinning, which results in low yield strength and large

uniform elongation through significant work hardening. Primary twinning and twin-twin intersection easily

undergo together with secondary twinning inside primary twins at the early stage of deformation. Our previous

work has reported that the {332} twinning is often activated with low Schmid factor and even with negative one

in a slightly deformed beta-type Ti-Mo polycrystalline alloy. Variant selection of these non-Schmid behaviors has

been qualitatively discussed in terms of local stress concentration and geometric constraint between neighboring

grains. The aim of present study is to further quantitatively analyze the variant selection of primary and secondary

twinning through accommodative strain combined with Schmid law. A beta-type Ti-Mo polycrystalline alloy was

subjected to tensile deformation. Deformation microstructure was observed with a field-emission scanning

electron microscope equipped with an orientation imaging system for conducting the electron backscattered

diffraction analysis with EDAX OIM analysis software. Accommodation strain was calculated by rotating the

twinning shear displacement gradient tensor expressed in the twinning system reference frame into the

crystallographic reference frame of neighboring grain or region. The results show that local stress concentration is

easily produced by interaction between twin and grain boundary, and by twin-twin intersection. The methods to

accommodate local stress concentration are plastic relaxation of dislocation slip or {332} twinning. Twinning

transfer occurs easily at low angle grain boundary, corresponding that either initial active twin or

accommodative twin with high Schmid factor. In case of high angle grain boundary, slip transfer and

accommodative twin with low Schmid factor are often present. Due to the twin-twin intersection, secondary

twinning forms inside primary twins even with negative Schmid factor. To quantitatively analyze the

accommodation strain, transformation matrix is calculated from activated twinning frame to twelve possible

accommodative twinning frame in the neighboring grain or region, and then the twinning shear displacement

gradient tensor is specified in the neighboring twinning variant. As a consequence, twinning variant has the

highest accommodative capacity to relax the local stress contraction, which results in the non-Schmid behavior.

Schmid factor, Accommodative strain, Primary twins, Secondary twins, Variant selection

F-P24

Effect of electron beam melting parameters on microstructure and element evaporation of Ti-Mo alloys

Kai Yao1, Xiaohua Min1, Shuang Shi1,2, Congqian Cheng1, Jie Zhao1, Yi Tan1,2

1. School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, P.R.C.

2. Key Laboratory for Solar Energy Photovoltaic System of Liaoning province, Dalian 116024, P.R.C

b titanium alloys are found wide use as structural materials due to their high specific strength and good corrosion

resistance. Based on the traditional melting technology for b titanium alloys, segregation of alloy elements,

inclusions and impurities easily occur which weaken their mechanical properties. The electron beam melting

(EBM) is an effective method for purifying solar-grade silicon, refining refractory metals and alloys due to its

high energy density and high vacuum. Preparation of Ti-6Al-4V alloy ingot by EBM has been industrialized.

However, little effort has been made using EBM technology to manufacture b titanium alloys. In the present work,

b-type Ti-Mo alloys were prepared by EBM and the influence of melting parameters on microstructure and

element evaporation were investigated.

Melting tests were conducted on a SEBM-60A electron beam melting furnace. Two different raw materials were

used in the test: one was pure titanium and pure molybdenum, and the other was pure titanium and Ti-32Mo

49

intermediate alloy. In the melting processes, the vacuum of the melting chamber was kept at 2-5×10-2 Pa, and the

electron beam gun chamber was maintained at 1-4×10-3 Pa. The electron beam current was turned off

instantaneously after melting to acquire a huge cooling speed. The compositions were analyzed by X-ray

fluorescence (XRF), and the microstructures were characterized by the optical microscope (OM).

There were continuous four-times melting using the pure titanium and pure molybdenum as raw materials:

electron beam currents of 300mA, 400mA, 350mA, 500mA for 10min,10min, 20min, 15min, respectively.

However, four melting failed to completely proceed due to the high melting point of molybdenum. Moreover, as

the increase of electron beam currents, the total mass loss rate increased from the 2.65% to 25.96%. The high

mass loss rate was mainly contributed to the loss of titanium for its high vapor pressure. With the pure titanium

and Ti-32Mo intermediate alloy as raw materials, the melting proceeded well under the electron beam current of

500mA for 10min. The total mass loss rate decreased compared with the former melting in the same condition,

while some stomatas formed at the bottom of the ingot.

Electron beam melting, b titanium alloy, Melting parameters, Microstructure, Element evaporation

F-P25

Dynamic compression properties of Ti-6Al-4V titanium alloy extruded sections

Rui Liu, Song-xiao Hui, Wen-jun Ye, Yang Yu, Xiao-yun Song

State Key Lab of Nonferrous Metals & Processes, General Research Institute for Nonferrous Metals, Beijing

100088, China

This paper aimed to study the dynamic compression properties of Ti-6Al-4V titanium alloy sections. The

Ti-6Al-4V sections were extruded above the β-transus temperature with extruding ratio of 85, and then heat

treated by conventional annealing at 750 ℃, or annealing at 1200 ℃ by two routes. The dynamic compression

properties were investigated by Split Hopkinson Pressure Bar system at strain rate of 3000±200 s-1. The results

show that the dynamic compression properties of as-extruded specimens are comparable to the specimens after

conventional annealing at 750 ℃. Compared to Widmannstatten microstructure with original beta grains in size

of 200 μm ~ 300 μm obtained by conventional annealing, the microstucture obtained by annealing at 1200 ℃

with coarse grains consisited of fine α-lamellae exhibits comparable dynamic strength but the capability of

plastic deformation reduces about 20%. For the microstucture obtained by annealing at 1200 ℃ with coarse

grains consisited of coarse α-lamellae, the dynamic strength slightly decreases, while the capability of plastic

deformation reduces about 60%.

titanium alloy, extruded section, dynamic properties

F-P26

Microstructure and mechanical properties of Ti-6Al-2Sn-4Zr-2Mo-1Nb-0.2Si high-temperature titanium

alloy plate

Xiaoyun Song, Yongling Wang, Wenjing Zhang, Wenjun Ye, Songxiao Hui

State Key Laboratory of Nonferrous Metals & Processes, General Research Institute for Nonferrous Metals

Ti-6Al-2Sn-4Zr-1Mo-2Nb-0.2Si (Ti62421S) alloy is a novel near-α high temperature titanium alloy, which has

huge utilization potentiality under 650℃ for short-time using. The β transus temperature was 1010~1020 ℃

tested by metallographic method. In this paper, three different double annealing treatments were applied on the

Ti62421S alloy plate with 3mm in thickness. Optical microscopy (OM), scanning electron microscopy (SEM),

transmission electron microscopy (TEM) and tensile tests are used to investigate the microstructure, phase

50

precipitation behavior and mechanical properties under different temperatures of Ti62421S alloy. The results show

that the hot-rolled alloy plate is composed of primary α phase (αp) and intergranular β phase, and the two phases

are both elongated along the rolling direction. After double annealing treatment, ordered α2 phase precipitates and

increase with first annealing temperature. This leads to that the room-temperature tensile plastisity for specimens

after double annealing is lower than that for single annealing. With increasing first annealing temperature,

ultimate tensile strength (UTS) at 550~650℃ increases while elongation decreases. After 1000℃/2h/AC+ 600℃

/2h/AC duplex annealing treatment, Ti62421S alloy plate showed superior tensile properties. The values of UTS

and elongation at room temperature reached 1075MPa and 10%, as well as the value of UTS at 650℃ exceeded

630 MPa which is at the same level with traditional long-time using high-temperature titanium alloy at 600 ℃.

High-temperature titanium alloy, duplex annealing treatment, microstructure, mechanical properties

F-P27

Effect of oxygen on β to ω phase transformation kinetics in Ti-Mo alloys

Li Xiang1, Xiaohua Min1, Satoshi Emura2, Congqian Chen1, Jie Zhao1, Koichi Tsuchiya2

1. School of Materials Science and Engineering, Dalian University and Technology, Dalian 116024, Liaoning,

China

2. Research Center for Structural Materials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba

305-004, Japan

beta-type titanium alloys have diversity of deformation mode and they lend themselves to strengthening by

controlling of their alpha-phase and omega-phase. It is generally accepted that athermal omega particles forms by

a diffusionless transformation during quenching, while isothermal omega phase forms by diffusion of solute atoms

after aging at a low temperature. Formation of omega phase is considerably depended on the nature of alloying

element. Addition of oxygen to beta titanium alloys acts as a barrier of isothermal omega phase transformation,

but some studies have reported that oxygen can stabilize isothermal omega phase. Thus, the role of oxygen on the

formation of isothermal omega phase remains controversy. The aim of this paper is to investigate the effect of

oxygen on formation of isothermal omega phase in a beta-type Ti-15Mo alloy and to discuss the phase

transformation kinetics. The ingots (approximately 1kg in each) of Ti-15Mo-xO (x=0.1-0.5, in mass%) alloys

were prepared by cold crucible levitation melting followed by homogenizing and hot forging at 1273K, and hot

rolling at 1173K. The rolled plates were solution treated at 1173K for 3.6ks followed by water quenching and

subsequent aged at temperatures from 573K to 773K for 3.6ks followed by water quenching. The samples were

subjected to OM and TEM observations, XRD phase identification, and DSC thermal analysis. Vickers hardness

was measured with a load of 9.8N at ten different positions, with their average taken as the value for that sample.

Both of solution-treated 0.1O and 0.5O alloy were comprised by beta grains without significant difference

between them. The hardness in solution treated 0.1O alloy was smaller than that of 0.5O. Peaks of omega phase

from XRD profiles did not detected in solution-treated 0.1O and 0.5O alloy, but they appeared when aging at

573K to 773K. The hardness increased with an increase of ageing temperature. The intensity of omega peaks

increased from 573K to 673K and decreased from 673K to 773K, while the incremental oxygen content caused a

clear decrease in the intensity of omega peaks. The DSC curves of 0.1O alloy showed an exothermic

transformation between 523K and 723K, and an endothermic transformation between 723K and 873K. The peak

of exothermic transformation in the curves of 0.5O alloy was smaller than that of 0.1O alloy, while the peak of

endothermic transformation had no significant difference between them.

β-type titanium alloys; Oxygen; ω phase transformation; Kinetics

51

F-P28

Hot Deformation Behavior and Processing Map of a New High-temperature Titanium Alloy

Shaohui Shi, Tao Li, Yongshuang Cui, Lihua Chai, Ziyong Chen

School of Materials Science and Engineering, Beijing University of Technology, Beijing 100124

Hot Deformation Behavior and Processing Map of a New High-Temperature Titanium Alloy

Abstract: Isothermal constant strain rate compression testing of a new as-cast high-temperature titanium alloy

Ti-6.5Al-2.5Sn-9Zr-0.5Mo-1W-1Nb-0.25Si-0.1Er alloy is carried out at the deformation temperatures range from

900 to 1100°C with 50 °C intervals, strain rate range from 0.001 to 1 s-1 and 60% of engineering strain. The

deformation behavior of this high-temperature titanium alloy is analyzed based on the stress-strain result,

meanwhile the constitutive equation based on the hyperbolic sine model and the parameters of Zener–Hollomon is

established, which show a close accordance with the experimental value. The hot processing map based on the

dynamic material model and the Prasad’s instability criterion is constructed at strains of 0.6. The map exhibit a

stable deformation domain in the temperature range of 940~960°C and strain rate range of 0.001~0.002S-1, and in

the temperature range of 1030~1070°C and strain rate range of 0.02~0.06S-1 with the power dissipation efficiency

respectively of 58.5% and 54.5%.

high-temperature titanium alloy, hot deformation, constitutive relation, processing map

F-P29

The effect of annealing on microstructure and tensile properties of Ti-6.5Al-2Sn-4Zr-2Mo-2Nb-1W-0.2Si

alloy

Wenjing Zhang

General Research Institute for Nonferrous Metals

The effects of single annealing on microstructure and mechanical properties of an (alpha+beta) titanium alloy

(Ti-6.5Al-2Sn-4Zr-2Mo-2Nb-1W+0.2Si) were studied by optical microscopy (OM), electron probe microanalysis

(EPMA) and tensile testing. The results showed that, with annealing temperature increasing, the volume fraction

of primary alpha phase decreased gradually, while the volume fractions of beta phase and secondary α phase

increased, and the size of these phases became coarse. Elevating the annealing temperature, the room temperature

strength increased at first and then decreased, the high temperature strength increased gradually, and the ultimate

tensile strength and yield tensile strength at 650℃ can reach more than 700 MPa and 500 MPa, respectively. The

room temperature ductility and high temperature ductility decreased with the annealing temperature increasing. In

order to acquire good strength at high temperature and plasticity at room temperature, the best annealing

temperature is 980℃.

titanium alloy,annealing temperature,microstructure,mechanical properties

F-P30

Effect of TiB on α phase nucleates and grows up in the Ti-6Al-4V alloy

Yang Yu, Xujun Mi, Songxiao Hui, Wenjun Ye

General Research Institute for Nonferrous Metals

Effect of TiB on IFN-alpha phase nucleates and grows up in the Ti-6Al-4V alloy were investigated by different

cooling microstructure of Ti-6Al-4V alloy and Ti-6Al-4V-0.1B alloy from the temperature above the phase

transition point , Pole figures of IFN-alpha phase, IFN-beta phase and TiB phase at different crystal plane by

52

EBSD . The results showed that during the cooling process from the temperature above the phase transition point,

IFN-alpha phase nucleates and grows up in the IFN-beta phase matrix and TiB phase. TiB phase as another

nucleation position of IFN-alpha phase is conducive for the nucleation and precipitation of IFN-alpha phase.

TiB;α phase ;nucleates ; grows up

F-P31

Microstructural evolution and phase transformation in gas atomized Ti-48Al powders

Dongye Yang1, Weijie Lu1, Ying Bao2, Na Liu3, Gouging Zhang3, Jianfei Sun2

1. Shanghai Jiao Tong University

2. Harbin Institute of Technology

3. Beijing Institute of Aeronautical Materials

The paper focuses on the microstructural evolution and phase transformation of undercooled Ti-48Al (at.%)

droplets atomized by high pressure gas. The solidified powders were quantitatively investigated using scanning

electron microscopy (BSE), transmission electron microscopy (TEM), electron back-scatter diffraction (EBSD)

and X-ray diffraction (XRD). Results showed that the powder microstructures were transformed from a twinned

spherical segment into a concentric liquid/solid interface geometry with increasing droplet size, and the

microstructural transition from cellular to dendritic can be identified as the cellular dendrites with a rosette

appearance. The primary phase, final phase volume fraction and the hardness are related to the droplets size to

provide fundamental understanding. The competitive formation of the primary phases α and β are strongly

controlled by the droplets size. The final phase volume fraction of γ increased with the increase of powder size

from 12% to 85%. The highest hardness with the value of 652 HV was obtained for powder of 50 μm in diameter.

TiAl alloy, Gas atomization, Rapid solidification, Microstructure, Phase transformation

F-P32

Effect of initial microstructures on hot deformation behavior of Ti-6Al-4V alloy

Zhi Xiong Zhang, Shou Jiang Qu*, Jun Shen

School of Materials Science and Engineering, Tongji University, Shanghai 201804, P.R. China.

Titanium alloys have been widely used in aerospace, energy, military, marine and medical industries. Due to its

specific high strength-to-weight ratio, good corrosion resistance and good biocompatibility, Ti-6Al-4V alloy has

been widely utilized for structural applications such as structural airframe, engine components, dental implants

and artificial joints. In order to control microstructure and to obtain attractive mechanical properties, titanium

alloys are deformed at relatively low temperatures. However, the hot workability of titanium alloys decreases with

the temperature decreasing. Thus, titanium alloys are considered to be difficult to process. Generally, the flow

behaviors of titanium alloys during thermo-mechanical processing (TMP) are significantly influenced by the

processing parameters such as temperature, strain and strain rate. In addition, the preform microstructure has an

important influence on the hot working behavior of these alloys. Extensive research has been carried out to study

Ti-6Al-4V alloy with various initial microstructure and processing conditions. In general, the thermomechanical

processing of Ti-6Al-4V alloys involves hot deformation above the β transus temperature to obtain a transformed

β microstructure, and then mechanical working in the α+β field to obtain equiaxed α+β structure. Thus, the effect

of various preform microstructures on hot deformation behavior of Ti-6Al-4V alloy in the α+β range is desired to

be studied.

Plastic flow behavior and microstructural evolution during subtransus hot deformation were investigated for

53

Ti-6Al-4V alloy with three different initial microstructures. These conditions consisted of a lamellar α+β

microstructure, a martensitic microstructure and a bimodal microstructure. The materials used in this present work

included a 355-mm-diameter as-casted bar stock of Ti-6Al-4V with a transformed β microstructure and a

80-mm-diameter hot-forged bar with a bimodal microstructure. The measured composition (in wt pct) of the

as-casted bar was 6.08 aluminum, 4.03 vanadium, 0.14 iron, 0.11 oxygen, 0.013 silicon, 0.018 carbon, 0.0047

nitrogen, 0.0008 hydrogen and balance titanium. The measured composition (in wt pct) of the as-forged bar was

6.27 aluminum, 4.25 vanadium, 0.17 iron, 0.11 oxygen, 0.022 silicon, 0.012 carbon, 0.006 nitrogen, 0.0031

hydrogen and balance titanium. The beta transus temperature was reported to be 975 oC for both two materials.

The as-forged bar was subjected to a heat treatment condition: reheating to 1010 oC and annealing for 30 min,

followed by water quenching to get a martensitic microstructure.

Isothermal, constant true strain rate compression tests were conducted on Ti-6Al-4V samples with three different

microstructures by using a Gleeble-3800 simulator over the temperature range of 800 to 850 oC and at constant

true strain rates 0.001, 0.01, 0.1, 0.5, 1 s-1. Cylindrical samples with 8 mm diameter and 12 mm length were used.

A chromel-alumel thermocouple welded on the cylindrical surface of the samples to measure the temperature. The

specimens were reheated to test temperatures at heating rate of 10 oC/s, held for 5 minutes to homogenize the

temperature throughout the sample, and then upset to a height reduction of 60 pct under constant true strain rate

conditions, followed by water cooling. The microstructure of the deformed specimens was examined by various

characterization techniques, such as optical microscopy (OM), scanning electron microscope (SEM, FEI Quanta

250), transmission electron microscopy (TEM, JEOL JEM-2100FX) and electron backscatter diffraction (EBSD,

Apollo 300). The specimens were electrochemical polished with a solution of 60% carbinol, 34% n-butanol and 6%

perchloric acid with a voltage of 30 V and a current of 80 mA for the OM, SEM, EBSD characterization. The

TEM foils were twin-jet electrochemical polished in a solution of 60% carbinol, 4% perchloric acid and 36%

n-butanol.

The results of this study were presented and discussed in two parts on flow stress behavior and microstructural

evolution. For the transformed β microstructure, continuous flow softening after a peak stress was observed at

strain rates slower than 0.01 s-1. At strain rates higher than 0.1 s-1, a rapid drop in the flow stress with strain or

broad oscillations were observed, which indicated the unstable plastic flow of the material. For both the bimodal

microstructure and the martensitic microstructure, all the curves showed a peak stress at very low strains followed

by extensive flow softening.

The microstructural evolution was observed. For the transformed β microstructure, in the ranges 800-850 oC and

10-3-10-2 s-1, globularization of lamellar structure occurred. And at the strain rates higher than 0.1 s-1, all the

micrographs of the specimens deformed in this regime exhibited flow localization bands. For the martensitic

microstructure, a homogenous refined equiaxed grained microstructure was obtained after hot deformation. And

the grain size decreased with the temperature decreasing and the strain rate increasing, and the smallest grain size

was obtained at the temperature of 800 oC and the strain rate of 1 s-1. As with the bimodal starting microstructure,

the microstructure after deformation was inhomogeneous, the lamellar structure fragmented and part of them

transformed into globular ones after globularization, a number of short α lamellae was retained.

In conclusion, this work presented the hot deformation behavior and microstructural evolution of Ti-6Al-4V alloy

with various starting microstructures. For the transformed β microstructure, both of the flow behavior and the

microstructural observations exhibited flow instabilities. This is the “unsafe” regime for the transformed β

microstructure. For the martensitic microstructure and the bimodal microstructure, all the flow curves showed

flow softening after a peak stress. A homogeneous equaixed fine grained (α+β) microstructure was produced by

using an initial martensitic microstructure, and this work suggested that the phase transformation of α´/α+β

significantly contributed to the microstructural refinement.

54

Ti-6Al-4V; Microstructure; Grain refinement

F-P33

High Temperature Titanium Alloys with Increased Strength and Structural Stability

Xun Wang, Lu Wang, Yidong Wu, Qinjia Wang, Tuo Wang, Xidong Hui

University of Science and Technology Beijing

Near-α titanium alloys is widely used for the turbine blades and discs, engine crankcases etc. due to their high

tensile strength, creep and fatigue resistance properties and structural stability at high temperature. To understand

the strengthening behavior and the effect of Nb to the mechanical properties at high temperature of 600℃, this

work comprehensively investigated the crystalline microstructures, mechanical properties and structural stability

of Ti-Al-Mo-Si-Nb alloys by means of high temperature tensile test, scanning electron microscopy (SEM),

transmission electron microscopy (TEM), X-ray diffractometer (XRD) and differential scanning calorimetry

(DSC). The results show that after being alloyed with certain amount of Si, the tensile strength is increased for

more than 10%. It is also shown that with the addition of Nb, the high temperature performance of the alloys are

enhanced obviously.

Near-α titanium alloys; Niobium; Structural Stability

F-P34

Improved formability of magnesium alloy sheet by co-extrusion processing

Junjie He, Bin Jiang, Xu Jun

State Key Laboratory of Mechanical Transmissions, College of Materials Science and Engineering, Chongqing

University

Based on the promotion of strain gradient during hot extrusion, three composite modes of Mg-3Al-Zn (AZ31)

alloy ingot were designed previously to introduce special interfaces to improve the final mechanical properties. In

addition, the final mechanical property processed by the various co-extrusion and conventional extrusion were

compared and evaluated in correlation with the microstructure and texture evolution. The results indicated that the

various designed interfaces had significant influence on the microstructure and texture modification by

influencing the effective strain during extrusion, and thus altered the final mechanical properties of the sheets. The

sheet extruded by dichotomy structure of AZ31/AZ31/AZ31 and the sandwich structure of AZ31/AZ31/AZ31

show more uniform fine grains and titled weaker basal texture, resulting in obtaining much higher formability

compared with the conventional extrusion sheet. While the interfaces introduced by benz-structure ingot seems

has no positive effect on the mechanical properties of the AZ31 sheet during extrusion. This study suggested that

the introduction of appropriate interface by co-extrusion was a simple but effective method to improve the

formability of AZ31 alloy sheet.

Co-extrusion; Microstructure; Texture; Strain gradient; Mechanical property.

F-P35

Effect of the precipitated phases on corrosion behavior of Mg-Y-Nd ternary alloy

Quantong Jiang1, Xia Zhao1, Kui Zhang2, Xinggang Li2, Jizhou Duan1, Baorong Hou1

1. Marine Corrosion and Protection Centre, Institute of Oceanology, Chinese Academy of Sciences

2. State Key Lab for Non-ferrous Metals and Process, General Research Institute for Non-ferrous Metals

55

Mg-5Y-xNd alloys (x=0.5, 1.0 and 1.5 wt.%) were investigated to reveal the influence of precipitated phase on

corrosion resistance. The microstructure, precipitated phases and corrosion behaviors of different samples were

analyzed by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-Ray Diffraction

(XRD). The volume fraction of Mg12(Y,Nd) phase increased with the addition of Nd-content, whereas the

Mg3(Y,Nd) phase decreased. The weight loss rate decreased from 10.9584 mg•cm-2•d-1 (23.0126 mm•y-1) to

6.2184 mg•cm-2•d-1 (13.0586 mm•y-1). The open circuit potential (OCP), potentiodynamic polarization curve,

electrochemical impedance spectroscope (EIS) and scanning kelvin probe (SKP) confirmed that the corrosion rate

of Mg-5Y-xNd alloy was arranged as: Mg-5Y-0.5Nd＞Mg-5Y-1.0Nd＞Mg-5Y-1.5Nd. This phenomenon was

mainly attributed that the Mg3(Y,Nd) precipitated phase with face-centered cubic lattice had a more positive

potential than Mg12(Y,Nd) phase with orthorhombic lattice. As a result, the Mg3(Y,Nd) precipitated phase acted

as the cathode of electrochemical reaction, accelerated the corrosion of Mg matrix more effectively than

Mg12(Y,Nd) phase.

Mg-Y-Nd alloy; Microstructure; Precipitated phase; Corrosion resistance; Electrochemistry

F-P36

Synergistic Effect of MoS2 and SiO2 as Nanoadditives Enhancing the Tribological Properties for

Magnesium Alloy–Steel Contacts

Hongmei Xie1,2, Bin Jiang1,3, Junjie He1, Xiaowen Yu1, Fusheng Pan1,3

1. College of Materials Science and Engineering, National Engineering Research Center for Magnesium Alloys,

Chongqing University, Chongqing 400044, China

2. 2College of Mechanical and Electriccal Engineering, Yangtze Normal University, Chongqing 408100,China

3. Chongqing Academy of Science and Technology, Chongqing 401123, China

The nano-MoS2, nano-SiO2 and their composite were employed as lubricating additives in the base oil and their

tribological properties were investigated using a reciprocating ball-on-flat tribometer for magnesium alloy–steel

contacts. The results demonstrated that a remarkable synergetic effect between the nano-SiO2 and the nano-MoS2

on improving tribological properties for sliding magnesium alloy surfaces, especially for combinative addition of

1.0wt% nano-MoS2 and 0.1wt% nano-SiO2 in the base oil. Such excellent lubricating performances of the

SiO2/MoS2 composite nanoparticles in the base oil derive from the synergistic lubricating actions of spherical

nano-SiO2 and nano-MoS2 platelets during the rubbing process. The wear mechanism of the SiO2/MoS2

composite nanoparticles was investigated, and the protective and filling effect of the nanoparticles improved

because of collaboration of nano-MoS2 and nano-SiO2.

Nano-MoS2;Nano-SiO2;Lubricant additive; Magnesium alloy; Tribological properties

F-P37

Influence of initial microstructure on the hot working flow stress of Mg–3Al–1Zn

yunteng liu1, tao lin1,3, jixue zhou1,4, di zhang1,2

1. Advanced Materials Institute Shandong Academy of Sciences

2. Shandong Jianzhu University

3. Shandong provincal Key Laboratory for High Strength Lightweight Metallic Materials (HLM)

4. Shandong Engineering Research Center for Lightweight Automobiles Magnesium Alloys

The hot working flow stress is examined for wrought and as-cast magnesium alloy AZ31, deformed in

compression. It is found that the hot deformation behaviour is sensitive to the deformation conditions, initial

56

microstructure. The peak stresses in compression are higher for as-cast material at low strain rates and high

temperatures, whereas they are higher for fine-grained wrought material at high strain rates and low temperatures.

Most noticeably in the compression of the wrought material, the shape of the stress–strain curves change

considerably as the temperature is reduced and the strain rate is increased. These key features of the deformation

behaviour are explained in terms of initial grain size, texture, twinning and dynamic recrystallization.

Hot working; Dynamic recrystallization; Magnesium alloy AZ31; Wrought; As-cast

F-P38

Influence of micro-arc oxidation on mechanical properties of AZ61 magnesium alloy extruded sheet

Jixue Zhou1, Baichang Ma1, Jinwei Wang1, Yanfei Chen1, Jie Ma1, Weihong Li1, Yuansheng Yang2

1. Advanced Materials Research Institute of Shandong Academy of Sciences

2. Institute of Metal Research, Chinese Academy of Sciences

3. Shandong Key Laboratory for High Strength Lightweight Metallic Materials

The morphology of micro-arc oxidation coatings on AZ61 alloy extruded sheet was analyzed by scanning electron

microscopy. The tensile strength and fatigue property of AZ61 alloy sheet treated with micro-arc oxidation was

investigated by static tensile test and fatigue test. And the fatigue fractograph was analyzed by stereomicroscopy

and scanning electron microscopy. The results show that the inner layer of micro-arc oxidation coating was

imporous and compact, and the compact layer had good ductility and good bonding to the substrates. The bonding

strength was high. Micro-arc oxidation treatment had no obvious influence upon the tensile strength and fatigue

property of AZ61 sheet.

AZ61 magnesium alloy extruded sheet , Micro-arc oxidation, Tensile strength, Fatigue property

F-P39

Protective ability of graphite powders on molten AZ91D magnesium alloy

Weihong LI1,2, Jixue ZHOU1, Baichang MA2, Jianhua WU1, Jinwei WANG2, Haihua ZHUANG2, Yuansheng

YANG3

1. Shandong Key Laboratory for High Strength Lightweight Metallic Materials, Advanced Materials Institute,

Shandong Academy of Sciences, Jinan 250014, China

2. Shandong Engineering Research Center for Lightweight Automobiles Magnesium Alloys, Advanced Materials

Institute, Shandong Academy of Sciences, Jinan 250014, China

3. Superalloy division, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016,Liaoning,

China

Abstract: Graphite powders were used to prevent a molten AZ91D magnesium alloy from oxidation and burning

in order to develop a new pollution-free protection method with low cost. The method is expected to have good

protective effect without

decreasing the mechanical properties of the alloy. The protective ability of graphite powders on the alloy was

investigated. Experimental results show that the graphite powders provide effective protection for the AZ91D melt.

The protective effect increases with the increasing of graphite powder amount and the decreasing of melting

temperature and holding time. The microstructure, chemical composition and material phase of the surface films

formed on the molten AZ91D alloy were analyzed using scanning electron microscopy, energy dispersive

spectrometer and X-ray diffraction. The results demonstrate that the surface films have two layers and mainly

contain elements of Mg, O, F, C and

57

Al. The outer layer is continuous and mainly consists of MgO and C, while the inner layer is discontinuous and

mainly consists of MgF2 and Mg17Al12. The protection mechanism of the graphite powders on the molten

magnesium alloy was also presented. The graphite powders react with the melt and the ambient atmosphere, thus

form a continuous and dense protective film on the melt surface, providing effective protection for the melt.

AZ91D magnesium alloy; graphite powders; surface film; protection machanism

F-P40

The microstructure evolution of the Mg-3Zn-0.5Er alloy during hot rolling

Jinxue Liu, Ke Liu, Shubo Li, Zhaohui Wang, Wenbo Du

College of Materials Science and Engineering, Beijing University of Technology

Abstract: The microstructure evolution of the as-rolled Mg-3Zn-0.5Er alloy (wt.%) has been investigated. The

results showed that the phase constituents of the sheet were composed of α-Mg and I-phase. The microstructure of

sheets transformed from the deformation twinning into dynamic recrystallization (DRX) grains. Furthermore, the

deformation twinning appeared again in the dynamic recrystallization grains during further hot rolling. It indicated

that twin was the main deformation mechanism and marginal dynamic recrystallization (DRX) occurred in

deformation twins at low strains. As the reduction reached 39.6%, the twin dynamic recrystallization (TDRX)

regions cluster and widen by consumption of the initial deformation twins, then formed shear bands. After the

reduction exceeded 66.3%,the microstructure of sheets were composed of equiaxed DRXed grains and fine twins.

Moreover, compared with the RD-ND plane, the RD-TD plane has a smaller average grain size, ultimately

reached ～15.8μm, which also led to a higher average value of the hardness.

Mg-3Zn-0.5Er alloy; rolling; Icosahedral quasicrystalline; twin

F-P41

Effects of Mn addition on the microstructure and mechanical properties of extruded

Mg-4Zn-2Al-2Sn-0.6Mn alloy

Dongqing Zhao1,2, Yuansheng Yang1,2, Jixue Zhou1,3, Xinen Zhang3

1. Shandong Key Laboratory for High Strength Lightweight Metallic Materials, Advanced Materials Institute,

Shandong Academy of Sciences

2. Institute of Metal Research, Chinese Academy of Sciences

3. Shandong Engineering Research Center for Lightweight Automobiles Magnesium Alloy, Advanced Materials

Institute, Shandong Academy of Sciences

The microstructures and mechanical properties of the extruded Mg-4Zn-2Al-2Sn (wt.%) (ZAT422) and

Mg-4Zn-2Al-2Sn-0.6Mn (ZATM4220) alloys have been investigated. The ZAT422 and ZATM4220 alloys were

prepared by semi-continuous casting. After homogenized at 608 K for 4 h and then 693 K for 4 h, the alloy bars

were extruded at 648K with an extrusion ratio of 61 and extrusion speed of 1～2 m/min. It was found that the

addition of 0.6wt.% Mn to the Mg-4Zn-2Al-2Sn alloy affected the extrusion microstructure significantly.

Compared to ZAT422 alloy, the dynamic recrystallization grains of ZATM4220 alloy got fined obviously, and the

{0002}<10-10> basal texture got weaken a little, which lead to the improvement of the mechanical properties of

the alloy. The yield strength, tensile strength and elongation of ZATM4220 reached to 226.2 MPa, 325.2 MPa and

23.8 %, respectively. After aging (T5) treatment, the yield strength of extruded ZAT422 and extruded ZAT4220

alloys both increased.

Mg-4Zn-2Al-2Sn alloy; Mn; microstructure; refinement

58

F-P42

The evolution of weak connection of FSW joints and active control by ultrasonic and heat pipe

Maoyou Xu, Sheng Lu, Jun Chen, Aoyun Shen

Material Science and Engineering Institute, Jiangsu University of Science and Technology, Zhenjiang 212003

This study is based on the idea of the ultrasonic vibration friction stir welding and the heat pipe was used to

control the temperature field. In order to eliminate the phenomenon of weak link and improve the microstructure

and property of AZ31 magnesium alloy joint by FSW, the ultrasonic vibration and heat pipe was applied to the

welding process. Respectively in friction stir welding, ultrasonic vibration condition, heat pipe/ultrasonic

vibration (air cooling) and heat pipe/ultrasonic vibration (water cooling at room temperature), the FSW

experiment were done. Furthermore, the evolution of weak connection of FSW joints will be researched through

contrastive analysis.

The result of vibration measurement shows that each measurement point temperature goes through a process of

increasing firstly and then decreasing. The starting measuring points of the each condition all present the “double

peaks” phenomenon. Compared with the FSW, the peak temperature of welding process that imposed with active

control had dropped, especially in the heat pipe with water cooling.

Microstructure analysis shows that ultrasonic vibration welding joint grains were fined apparently, especially in

the nugget zone. There are all the small equaled grains. While Ultrasonic and heat pipe were applied together,

especially in water conditions, the size of the grains in upper part of nugget zone is obvious refined. Meanwhile,

the heat affected zone is narrowed even disappear.

Hardness test shows that the micro-hardness curve presents an asymmetric “W” type distribution. There is no

clear improvement for the nugget zone when applying ultrasonic vibration and heat pipe, however, the ultrasonic

and heat pipe have an advantage effect to the hardness of zone in advancing side.

The tensile test shows that there is no obvious effect on the tensile strength of welded joints in different conditions.

But the plasticity of the ultrasonic vibration joints was improved greatly.

By exerting the ultrasonic and heat pipe to FSW process, the quality of welded joint has been improved

significantly. The effect of ultrasonic vibration promotes the flow of the welding metal and the heat pipe improves

the asymmetry of welding temperature field between advancing side and retreating side.

AZ31Mg; Friction Stir Welding; Ultrasonic Vibration; Heat Pipe; Temperature Field

F-P43

Effect of graphite powder amount on the surface films formed on molten AZ91D magnesium alloy covered

by graphite powders

Weihong LI1, Jixue ZHOU1, Baichang MA2, Jianhua WU1, Jinwei WANG2, Haihua ZHANG2, Yuansheng YANG3

1. Shandong Key Laboratory for High Strength Lightweight Metallic Materials, Advanced Materials Institute,

Shandong Academy of Sciences, Jinan 250014, China

2. Shandong Engineering Research Center for Lightweight Automobiles Magnesium Alloys, Advanced Materials

Institute, Shandong Academy of Sciences, Jinan 250014, China

3. Superalloy division, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016,Liaoning,

China

Graphite powders were used to prevent a molten AZ91D magnesium alloy from oxidation and burning. The

graphite powders with the amounts of from 0 g•dm-2 to 10.8 g•dm-2 were used to form surface films on the

59

molten alloy at 700 ℃ for 30 min. The microstructure, chemical composition and material phase of the surface

films were analyzed using scanning electron microscopy, energy dispersive spectrometer and X-ray diffraction.

The effect of graphite powder amount on the characteristics of the surface films was studied and the influence

mechanism was discussed. Experimental results show that the surface films have two layers and mainly contain

elements of Mg, O, F, C and Al. The outer layer is continuous with thickness of 200 nm～550 nm and mainly

consists of MgO and C, while the inner layer is discontinuous and mainly consists of MgF2 and Mg17Al12. With

increasing the graphite powder amount, the compactness of the outer continuous layer increased, while the

continuity of the inner layer increases at first and then decreases. The graphite powder amount has effects on the

characteristics of the surface films by affecting the reactions between the graphite powders, the melt and the

ambient atmosphere.

AZ91D magnesium alloy; graphite powders; surface film; protection machanism; amount

F-P44

Microstructure and mechanical property of a Mg-Gd-Y-Zn-Zr alloy processed by 8-pass equal channel

angular pressing

Huan Liu1,2, Lepeng Jia1,2, Cheng Li2, Jinghua Jiang2, Ma Aibin1,2

1. Ocean and Coastal Engineering Research Institute, Hohai University

2. College of Mechanics and Materials, Hohai University

In this work, a high-strength Mg-10Gd-2Y-1.5Zn-0.5Zr (wt.%) alloy was prepared via 8 passes equal channel

angular pressing (ECAP). The microstructures and mechanical properties of as-cast and ECAP alloys were

systematically investigated by x-ray diffractometer, optical microscopy, scanning electron microscopy,

transmission electron microscopy and electronic universal testing machine. The obtained results show that the cast

alloy is composed of a-Mg dendrite, skeleton Mg3Gd phase, and lamellar 14H long period stacking ordered

(LPSO) phase which is precipitated near the boundary of Mg3Gd. After 8 passes ECAP, the skeleton Mg3Gd

phase is deformed and broken. However, the refined Mg3Gd particles are not distributed uniformly in the matrix,

but still aggregated at the interdendritic area. As for 14H LPSO lamellas, they become bent and kinked, but not

broken under severe deformation, suggesting good plasticity of LPSO phase. Compression test at room

temperature indicates that the ECAP alloy exhibits excellent mechanical property with compressive strength of

518 MPa and fracture strain of 21.6%. The comprehensive high strength and toughness of ECAP alloy could be

ascribed to the refined Mg3Gd particles, DRX grains, and kinked 14H LPSO phase.

Mg-Gd-Y-Zn-Zr; Long period stacking ordered (LPSO) phase; Equal Channel Angular Pressing (ECAP);

Compression strength; Fracture strain

F-P45

High Strength Mg94Zn2.4Y3.6 Alloy with Long Period Stacking Ordered Structure Prepared by

Near-rapid Solidification Technology

Jian zhu1, Jinbin Chen1, Ting Liu1, Junxiu Liu2, Williamyi Wang3, Zikui Liu3, Xidong Hui1

1. State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing

2. Department of ENT, Peking University Third Hospital

3. Department of Materials Science and Engineering, The Pennsylvania State University

To obtain high strength for Mg alloys by an easy near-rapid solidification (NRS) technology, the microstructures

and mechanical properties of Mg94Zn2.4Y3.6 alloy, which were prepared by ordinary and injection copper mold

60

casting (ICMC), were investigated comprehensively. It has been shown that the microstructure of ICMC

Mg94Zn2.4Y3.6 alloy is of the far-away-from equilibrium feature of NRS materials, which consists of refined

α-Mg grains with supersaturated Y and Zn, fine network-like long-period stacking-order (LPSO) phases and a few

Mg24Y5 particles. Semi-coherent interface between LPSO phase and α-Mg matrix has been formed, of the

orientation relationship is [0002]α∥[1120]LPSO, (1010)α∥(0002)LPSO. The ICMC alloy exhibits enhanced

mechanical properties with the tensile strength and elongation up to 355 MPa and 7% at room temperature, and

302 MPa at 150 °C, respectively. It can be concluded that the strengthening mechanisms of this ICMC alloy are

attributed to grain refinement, the solid solution, secondary phase precipitation and crystalline boundaries

strengthening.

Mg-Zn-Y alloy, Long Period Stacking Ordering, Near-rapid Solidification, Mechanical Properties.

F-P46

Effect of cooling rate on the microstructure of Mg-8Gd-1Er as-cast alloy

Yue Zhang, Wenbo Du, Xiaobing Zheng, Ke Liu, Zhaohui Wang, Shubo Li, Xian Du

Beijing University of Technology

Abstract: The effect of cooling rate on the solidified microstructure of Mg-8Gd-1Er (wt.%) alloy was studied by

using the microstructure observation and steady state nucleation theory. The results suggested that the increase in

cooling rate refined the grain size obviously because of the increment of the nucleation undercooling. As the

cooling rate increased, the primary α-Mg solid solution phase transformed from the coarse phases into the fine

dendritic crystal. In addition, the secondary phase of Mg5Gd phase distributed more homogeneously as the

cooling rate increased, but its volume fraction decreased because of the difficulty in the diffusion of solute atoms.

The presence of a quite small amount of Mg3Gd phase as the cooling rate increased, owning to un-equilibrium

solidification in Mg-8Gd-1Er alloy.

Mg-Gd-Er alloy;Cooling rate;Microstructure;Nucleation analysis

F-P47

The microstructure and creep behaviors of cast Mg-Zn-Er alloys

Ruijing Li, Shubo Li, Ke Liu, Zhaohui Wang, Xian Du, Wenbo Du

Beijing University of Technology

Key words: Mg-Zn-Er alloy; I-phase; creep resistance; microstructure

Abstract ：The microstructure and creep behaviors of cast Mg-xZn-yEr (x=3,6,9 wt.% ,x/y=6) alloys were

investigated by X-ray diffraction (XRD), optical microscope (OM), scanning electron microscope (SEM) and

transmission electron microscope (TEM). The XRD results indicated that the main phase compositions of the

as-cast Mg-xZn-yEr alloys were the I-phase and the α-Mg solid solution. The I-phase was mainly distributed in

the inter dendritic and staccato strips. The creep tests were conducted under the condition of 448K,70MPa for

100h. The results showed that the total creep strain decreased from 0.962% to 0.512% and the steady state creep

rate decreased from 1.411×10-6s-1 to 4.917×10-9s-1 when the addition of Er increased from 0.5 wt.% to 1.5 wt.%.

With the volume fraction of I-phase increased, the I-phase had a tendency to become bulky and continuous. The

appearance of the creep strain was attributed to the I-phase, which effectively blocked the movement of

dislocations to strengthen the as-cast Mg-Zn-Er alloys and improved the creep resistance. The creep mechanism of

the as-cast alloy was mainly grain boundary slipping.

61

F-P48

Sol-gel method to ceria coatings on AZ91 magnesium alloy

Huimin Han, Dantong Wang, Huaqian Yu, Min Zuo

University of Jinan

In this paper, the ceria coatings on AZ91 substrates were successfully synthesized by chemical conversion, in

which Ce(NO3)3•6H2O was used as resources. What is more, the corrosion resistance of AZ91 samples without

and with ceria coatings all were evaluated by means of electrochemical corrosion on in 3.5 wt.% NaCl solution.

According to the parameters derived from the polarization date, the Icorr (the corrosion current density) values of

the coated samples are smaller than that of bare one, indicating that the corrosion resistance of AZ91 alloys has

been improved to some extent. Meanwhile, the effects of the pretreatment of fluoride, inter-layer heat treatment,

sintering temperature and the layer of films on the performance of ceria coatings were also investigated. The

optimal parameters of the ceria coating were three layers on hydrofluoric-acid chemical pretreated substrate

without inter-layer heat treatment and the sintered temperature was 350 ℃. The Icorr of optimal sample is about

0.0219mA/cm2, which decreases by two orders of magnitude compared with the bare one. Based on the results,

this new environmental-friendly surface treatment of the ceria coatings has significant improvement on the

corrosion resistance of AZ91 magnesium alloy.

AZ91 alloy; Ceria coating; Sol-gel; Corrosion resistance; Tafel curve

F-P49

High-strength Mg-Zn-Mn-Sn wrought alloy

Fugang Qi1, Wenzhong Luo1, Dingfei Zhang2,3, Xingxing Xu2,3

1. School of Materials Science and Engineering, Xiangtan University, Xiangtan, 411105, P.R.China

2. College of Materials Science and Engineering, Chongqing University, Chongqing, 400045, P.R.China

3. National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing, 400044,

China

The microstructure and mechanical properties of the Mg-8Zn-1Mn alloys with varying Sn contents subjected to

the extrusion and T6 treatments were investigated by optical microscopy (OM), X-ray diffractometer (XRD),

transmission electron microscopy (TEM) and uniaxial tensile test at room temperature, respectively. The results

show that T6 treatments, especially double aging, can significantly increase the strengths of the extruded alloys.

Among them, the Mg-8Zn-1Mn-4Sn alloy with double aging exhibits an ultimate tensile strength of 416MPa, a

0.2% yield strength of 393MPa and an elongation of 5.29%. The microstructure characterization suggests that the

high strengths of the peak-aged alloys are attributed to the combined precipitation strengthening of the fine and

dispersed β1′ (MgZn2) and Mg2Sn precipitates.

Mg-Zn; Mg-Sn; Precipitate; Mechanical properties

F-P50

Study on the material flow of ultrasonic friction stir welding of magnesium alloy

Jun Chen, Sheng Lu, Maoyou Xu, Aoyun Shen

Material Science and Engineering Institute, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu

212003, China

This article provides a method to weld multilayer thick plates including four pieces of 1mm AZ31 magnesium

62

plates and three pieces of 0.1mm copper-foils overlapping mutually by friction stir welding accompanying

ultrasonic vibration as well as a research of material flow in friction stir welding in magnesium alloy in the

direction of thickness. Simultaneously, the effects of ultrasonic vibration on microstructure and mechanical

properties in the joints of friction stir welding are discussed.

The results show that material flow field in the stir zone is divided into different zones, in which the direction of

plasticized metal flow is different but has respective rule, in the cross section and longitudinal section. In

advancing side, part of the plasticized metal flows downwards because of the stress of the shoulder, another part

moves upwards along the non-plasticized metal from bottom to top. In the retreating side, the majority of plastic

metal is squeezed into retreating side following the pin, the other flows to the advancing side with the shoulder.

The grain size grade of stir zone in ultrasonic friction stir welding is 8.5, in conventional friction stir welding is

8.2. This result indicates that ultrasonic vibration can refine the grains effectively, making the grains in the nugget

zone more refined, and makes the distribution of the grains more uniform. The microhardness of the joint in

ultrasonic friction stir welding is higher than that in conventional friction stir welding. Because grains refined by

ultrasonic vibration can lead to hardness enhancement. Finally ultrasonic vibration eliminates defects disappeared

in the joint of conventional friction stir welding significantly.

Friction stir welding, Ultrasonic vibration, Material flow, Microstructure, Mechanical properties

F-P51

Simulation of dynamic recrystallization of AZ31 magnesium alloy during hot deformation based on a

modified cellular automaton

Yongjian Wang 1, Jian Peng 1, 2*, Liping Zhong 1, Fusheng Pan 1,2 1. State Key Laboratory of Mechanical Transmission, College of Materials Science and Engineering, Chongqing

University, Chongqing 400044, China

2. Chongqing Academy of Science and Technology, Chongqing 401123, China

The hot deformation behavior of the homogenized AZ31 magnesium alloy was simulated using a modified

cellular automaton (CA) model in this paper and the experimental study was conducted simultaneously to verify

the accuracy of the simulated results. Based on the discrepancy between the experimental and simulated stresses,

the dynamic nucleation was determined via "midpoint method" in the built model. The simulated results, in terms

of stress, recrystallization fraction and microstructure, get a remarkable agreement with the experimental results,

indicating the modified model can be used to predict the hot deformation behavior of AZ31 alloy. Both of the

simulated and the experimental microstructure show the typical "necklace" structure when the corresponding

Zener-Hollomon value (Z) is low. The significant relationships between the nucleation number, the Z value and

strain reveal that the nucleation rate during hot working is not constant. The higher the Z value is, the more the

nucleation number has, the greater the degree of curve fluctuations is. Considering the competition between

nucleation and grain growth in the recrystallization process, it is attributed to the transforming from

nucleation-dominated to growth- dominated, in which the results refined recrystallized grain.

F-P52

Effect of aging treatment on the microstructure and thermal conductivity of Mg-12Gd alloy

Liping Zhong1, Jian Peng1, 2*, Yongjian Wang1, Fusheng Pan1,2 1. State Key Laboratory of Mechanical Transmission, College of Materials Science and Engineering, Chongqing

University, Chongqing 400044, China

2. Chongqing Academy of Science and Technology, Chongqing 401123, China

63

The microstructure and thermal conductivity of Mg-12Gd alloy aged at 498K were systematically studied in this

paper. The results show that with the increasing aging time, the second phase gradually become coarse and the

thermal conductivity increases. At the early stage of aging, there are large amount of precipitates in the α-Mg

matrix, but with the increasing aging time, the thermal conductivity of alloy increase very slowly, which is

attributed to the coherent interface between precipitates and matrix. At the aging time of 8-24h, thermal

conductivity increases linearly with time. Micro-hardness of alloy increases to the peak at 98.5±3.6HV and

thermal conductivity is 56.9 W/(m•K) after aging for 24h. Thermal conductivity increases to the peak at 75.7

W/(m•K) at aging time of 300h. Thermal conductivity of Mg-12Gd alloy is related to the volume fraction of

precipitates and the interface between precipitates and α-Mg matrix.

F-P53

Diffusion bonding of Ti-45Al-7Nb-0.3W alloy by spark plasma sintering

Kun Zhao, Yong Liu, Bin Liu

State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, PR China

Spark plasma sintering (SPS) is a new method for diffusion bonding of TiAl alloys. A powder metallurgical (PM)

Ti-45Al-7Nb-0.3W (at%) alloy was bonded using SPS. The effects of bonding temperature, pressure and time on

the microstructure and mechanical properties of the alloy were investigated. Complete metallurgical bonding can

be produced at temperatures above 1150 ◦C. The tensile strength of specimens depends on the percentage of

metallurgical bonding and the interfacial microstructure, and it can exceed the strength of the base material. The

fracture mode changes with bonding temperature, transforming from intergranular fracture at the bonding

interface to cleavage fracture in the substrate. Due to the activation process of SPS, metallurgical bonding can be

achieved at a lower pressure and shorter time than those of the traditional diffusion bonding process.

TiAl, intermetallics, Spark plasma sintering, Diffusion bonding, Mechanical property, Microstructure

F-P54

Experimental study on the dynamic tensile behavior of Ti-47Al-2Nb-2Cr-0.2W at elevated temperatures

Sihui Ouyang, Yong Liu*, Bin Liu, Xiaopeng Liang, Ziyang Gan

State Key Lab of Powder Metallurgy, Central South University, Changsha 410083, PR China

Split Hopkinson tension bar experiments were conducted to explore the mechanical behavior and deformation

mechanism of extruded Ti-47Al-2Nb-2Cr-0.2W(wt.%) alloy with near lamellar(NL) and duplex(DP)

microstructures under deformation at high strain rates of 800s-1 and 1350s-1. Deformed microstructure

observation was characterized by scanning electron microscopy, electron back scattered diffraction technique,

transmission electron microscopy. The testing results indicated that the alloy are both temperature and strain rate

dependent and they have a similar dependence, the Brittle to Ductile Transition Temperatures(BDTT) increase

with increasing strain rates and the comprehensive properties at elevated temperatures under dynamic loadings are

better than those under quasi-static loadings．In addition，the work-hardening rates under dynamic loadings are

independent of temperature and strain rate． It can be concluded that Ti-47Al-2Nb-2Cr-0.2W alloy is a

high-velocity ductile material.

TiAl-based intermetallics, Dynamic response under elevated temperature, Deformation mechanism

F-P55

64

Characterization of fatigue properties of powder metallurgy titanium alloy

Yuankui Cao1, Bin Liu1, Yong Liu1*, Ziyang Gan1, Huiping Tang2

1. State Key Lab of Powder Metallurgy, Central South University, Changsha 410083, PR China

2. State Key Lab of Porous Metal Materials, Northwest Institute for No-ferrous Metal Research, Xian 710016, PR

China

The fatigue characteristics of powder metallurgy (P/M) Ti6Al4V (wt%) alloys prepared by powder sintering and

hot rolling were studied under tension–tension loading conditions at R=0.1 and 25 Hz in air, where R=σmin/σmax

(σmin and σmax are the applied minimum and maximum stresses, respectively). The results show that for the

as-sintered Ti6Al4V alloy the fatigue limit is about 325 MPa, and the fatigue cracks initiate from the residual

pores open to the surface of the gauge area and propagate along the α/β interfaces. Hot rolling markedly enhances

the fatigue properties, and the fatigue limit increases to about 430 MPa. The reducing of porosity and refining of

grain size through hot rolling are the dominant mechanisms for the improvement of fatigue properties. In addition,

the microstructure of α/β interfaces//RD and the texture of <0001>α//RD formed during hot rolling act as barriers

for the fatigue crack propagation, which partly attributes to the improvement of the fatigue properties.

titanium alloys, powder metallurgy, hot deformation, fatigue, microtexture

Published only Effects of Ultrasonic Impact Treatment on the Residual Stress and the Microstructure of TA15 Welded

Joint

Guanglu Qian, Xiaoyun Song, Teng Ma, Songxiao Hui, Wenjun Ye

State Key Laboratory of Nonferrous Metals & Processes, General Research Institute for Nonferrous Metals

Residual stresses exist in all manufacturing processes which use heat and/or force such as casing, forming,

machining and welding.The effects of ultrasonic impact treatment on the distribution of residual stress and on the

microstructure of TA15 (Ti-6.5Al-2Zr-1Mo-1V) alloy joints by electron beam welding(EBW) were investigated.

The residual stress in fusion zone was mainly tensile stress and the maximum longitudinal stress value was

817MPa. After ultrasonic impact treatment, the residual stress near the welded joint exhibited a uniform

distribution and the maximum stress dropped to -153MPa, successfully introduced compressional stress on welded

joint. A marked microstructural change occurred after welding, with martensite in the fusion zone (FZ). No

significant change occurred in microstructure after ultrasonic impact treatment.

TA15 titanium alloy, Ultrasonic peening, Residual stress, Microstructure

Effect of deformation temperature on texture evolution of TLM titanium alloy

Xinfang Bai, Yongqing Zhao, Bo Li

Northwest Institute for Nonferrous Metal Research

The TLM alloy, with a nominal chemical composition of Ti-3Zr-2Sn-3Mo-25Nb (wt.%), is a near β type

biomedical titanium alloy independently designed and developed by Northwest Institute for Nonferrous Metal

Research in China. It possesses lower elastic modulus (E) values, excellent strength and toughness，better wear

resistance and fatigue that offers a good combination of the safety and quality for implanting. Intensive

investigations have been focused on this TLM alloy regarding such scientific aspects that processing route, phase

transformation and microstructure, mechanical properties, biocompatibility of micro-arc oxidation film on

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titanium alloy surface, etc. However, the texture developed in the TLM alloy during hot processing does have

notyet been studied so far.A complete understanding of the physical and metallurgical phenomena, then the

developed microstructure and texture, occurring in the processing is crucial to control the final properties of the

alloy. The present study was carried out to clarify the effect of the deformation temperature on the texture

evolution of TLM alloy, aiming at improving the mechanical properties for biomedical applications. Firstly, the

hot deformation texture under the different deformation temperature was measured by using X-ray diffraction,

followed by a discussion of the potential mechanism of the deformation texture evolution.

The result shows that TLM alloy of hot deformation consist of β phase only, and {111}, {001}, {001} and {111}

of β phase are the main texture at the different temperature from 750°C to 850°C. Meanwhile, the texture of

TLM alloy changes obviously with the increasing of deformation temperature. The {111} texture shows the

feature weakened firstly and then strengthened, while the {111} texture strengthened firstly and then weakened.

Speci as received, and is the nearly level of orientation density at the deformation temperature of 850°C.

TLMtitanium alloy; Texture; Hot compression test; {111} orientation

Improved formability of AZ31 layer in the composite sheet achieved by the co-extrusion

Qinghang Wang1, Bin Jiang1,2, Yanfu Chai1, Shaoxing Ma1, Jun Xu1, Fusheng Pan1,2

1. State Key Laboratory of Mechanical Transmissions, College of Materials Science and Engineering, Chongqing

University, Chongqing, 400044, China

2. Chongqing Academy of Science and Technology, Chongqing, 401123, China

In the present study, an effective extrusion approach called the co-extrusion was carried out to produce two

composite sheets. The microstructures, textures and mechanical properties of AZ31 layer in AZ31/AZ61 and

AZ31/Al laminate obtained by the co-extrusion process at room temperature were investigated. The results

demonstrated that the ductility and the ultimate tensile stress (UTS) of AZ31 layer in AZ31/AZ61 laminate were

higher than those of others at room temperature. Additionally, the yield strength of AZ31 layer in AZ31/AZ61

laminate was lower than that of others at room temperature. The improvement of formability of AZ31 layer in

AZ31/AZ61 laminate was mainly attributed to basal texture weakening in the composite interface. The difference

of texture feature in the composite interface of three composite sheets depended on additional shear deformation

which was caused by difference of flow rate of the composite interface. The soft AZ31 alloy was composed to the

intensive compression and shear strain by the relatively hard AZ61 alloy. The shear deformations in the composite

interface of AZ31/Al laminate was weaker than that of AZ31/AZ61 laminate.

Composite sheet; Shear deformation; Co-extrusion; Basal texture; Mechanical properties

Comparison the bending behaviors of extruded plate in different extrusion process and material

combination

Yanfu Chai, Bin Jiang

College of Materials Science and Engineering, National Engineering Research Center for Magnesium Alloys,

Chongqing University

Fabricating the Mg-3Al-Zn/ Mg-3Al-Zn, Mg-3Al-Zn/Al plate by the composite extrusion, compared with simple

Mg-3Al-Zn plate fabricate by convention extrusion. The microstructure, texture and properties of the above three

sheets were studied. Then the bending behaviors of AZ31, AZ31/AZ31, AZ31/Al were studied under uniform

testing conditions (Mg layer in tension). Finally, the experiment results show that the load–displacement curve is

related to the initial extruded sheets. When

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AZ31/AZ31 in contrast with simple AZ31, although both of them failure behaviors, but the load of AZ31/AZ31 is

obviously small than simple AZ31 plate. It’s ascribed to the different microstructure and texture in extrude plate.

Ultimately, affect the tension and compression asymmetry of the sheet. When AZ31/Al compared with

AZ31/AZ31, AZ31/Al display the best bend behavior and without failure behaviors from beginning to end. On the

one hand, the change of organization performance of Mg layer is due to the different flow degree of hard and soft

materials. On the other hand, it also influences the neutral layer of offset and the K value.

bending behaviors, extruded plate , texture, K value

Microstructure and mechanical properties of Mg-Er-Zn alloys with LPSO phases

Shujing Cui1, Xiangwei Wu1, Peng Jia1, Chen Wu1, Haoran Geng1,2

1. School of Materials Science and Engineering, University of Jinan, Jinan 250022, China

2. Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials, University of

Jinan, Jinan 250022, China

The long period stacking ordered (LPSO) phase can effectively increase the mechanical properties in term of the

increased critical resolved shear stress of basal or non-basal slip. Especially, the LPSO phase can exhibit high

strength, high ductility and deformability. It has been reported that the addition of Zn can further remarkably

enhance mechanical properties of Mg-RE (RE=Y, Gd and Ho etc.) based alloys, because the appreciate amounts

of Zn addition could lead to the formation of other strengthening phases, such as I phase, W phase and LPSO

phase. In order to research the effect of the addition amount of Zn on the microstructure and mechanical

properties of the Mg-Er-Zn alloys with LPSO phases. In this paper, the as-cast Mg(100-x-y)ErxZny(2, 0; 2, 1; 2, 2; 3,

0; 3, 1; 3, 1.5; 3, 2) alloys were prepared by the cast ingot metallurgy process. The effect of Zn on the

microstructure and phase composition of the alloys was studied by optical microscope (OM), scanning electron

microscope (SEM) with scanning electron microscope (EDS), X-ray diffraction (XRD) and transmission

electronic microscope (TEM). The investigation revealed the as-cast Mg98Er2 and Mg97Er3 mainly consisted of α

-Mg phases and Mg-Er eutectic phases. After adding Zn, the second phase changed obviously, When the atomic

ratio of Er/Zn =1, there are Mg-Er-Zn eutectic phases formed; when the 1< Er/ZnLPSO phases distributed near

the grain boundaries and herringbone W phases distributed between the LPSO phases formed; when the Er/Zn=2,

there are small amount of acicular LPSO phases without W phases formed, furthermore, the amount of LPSO

phases increased with the amount of Er and Zn; when the Er/Zn>2, there are a large amount of lamellar LPSO

phases formed. The tensile tests were elevated by WDW-100A and the results showed that the yield, tensile

strength and elongation of Mg96Er3Zn1 alloy at peak are 187.6MPa, 213Mpa and 13.7%, respectively. The Brinell

hardness of Mg96Er3Zn1 at peak is 70.9HB. The morphology and the amount of LPSO phases are mainly

responsible for the improvement of mechanical properties.

Magnesium alloys; Microstructure; Mechanical properties; Long period stacking ordered

Effect of cooling rate on hot tearing behavior of Mg-9Al-1Zn-0.8Ce alloy

Wenjun Liu1,2, Bin Jiang1,2, Suqin Luo2, Jun Xu1, Fusheng Pan1

1. College of Materials Science and Engineering, Chongqing University, Chongqing 400030, China

2. Chongqing Academy of Science and Technology, Chongqing401123, China

In this study, the influence of cooling rate (1.5, 0.3 and 0.1 °C/s) on the hot tearing susceptibility (HTS) of

Mg-9Al-1Zn-0.8Ce alloy was investigated by taking advantage of numerical simulation and experiment methods.

The filling and solidification behavior of casting are observed directly using AnyCasting software to predict the

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location and mechanism of cracks formation in constrained rod. The results demonstrate that the enhancement of

cooling rate could increase the residual melt modulus and volume, expand the distribution area of isolated pools,

and final result in large strain and stress concentration to decrease the hot tearing resistance during solidification.

Microstructure evolution and cooling curves are checked to help analyzing the experimental results. The

maximum value of HTS turned up at the cooling rate of 0.1 °C/s owing to the coarse microstructures and bulk

Al11Ce3. And the minimum value of HTS appeared at the rate of 1.5 °C/s thanks to the finest microstructures

and a large amount of eutectic. With the increase of cooling rate, hot tearing susceptibility of the alloy shows a

rapidly reduce at beginning, and a slow decline followed. Besides, morphology of fracture surface and distribution

of secondary phase were further discussed.

Mg-Al-Zn-Ce alloy, numerical simulation; solidification, cooling curves, fracture morphology

Effect of different local strains on the texture and mechanical properties of AZ31 magnesium alloy

produced by asymmetric extrusion

Jun Xu, Bing Jiang, Junjie He, Yanfu Chai, Qinghang Wang

College of Materials Science and Engineering, National Engineering Research Center for Magnesium Alloys,

Chongqing University

The different local strains induced in the microstructural inhomogeneity of AZ31 alloy subjected to direct

extrusion was studied using 3 asymmetric extrusion tool steel dies（AMT1, AMT2, AMT3）. Finite element

analysis of this asymmetric extrusion process was also conducted to investigate the temperature evolution，

effective stress，effective strain rate, and effective strain distribution, which were then conjunction with the

experiments results. Asymmetric extrusion was carried out to obtain the additional asymmetric local strains

throughout the sheet thickness direction. This enforced the crystallographic reorientation of (0002) basal planes

and changed the grain size. The corresponding mechanical properties have been modified. The basal texture of

AMT2 sheet was weakest compared with other asymmetric extrusion tool steel dies, as a result of the mechanical

properties was improved.Therefore, the AMT2 processing could be effectively improved the mechanical

properties of AZ31 magnesium alloy sheets.

AZ31 alloy Finite element analysis extrusion Texture Microstructure

Effect of Nd on the microstructure, mechanical and corrosion properties of Mg-Zn-Y-Nd alloys

jinyang zhang, Xinying Teng, Min Zuo

School of Materials Science and Engineering， University ofJinan， No.336， West road of Nan Xinzhuang, Jinan

250022, People's Republic of China

Objective： In this work, the Nd was added into the Mg-Zn-Y alloy to observe the microstructure transition of

LPSO phase in order to improve the stability of Mg-Zn-Y-Nd alloy. At the same time, the effect of the structure

transition on the mechanical properties and the corrosion resistance of Mg-Zn-Y-Nd alloy were also studied.

Methods： Phase structure of the alloy was identified by X-ray diffraction (XRD, Rigaku D8 Advance). The

formation of phase and thermostability of the alloy was studied by differential scanning calorimeter (DSC) at

20K/min. The morphology was determined by a scanning electron microscope (SEM, FEI QUANTA FEG 250)

coupled with an energy dispersive X-Ray spectroscopy (EDS) for elemental analyses. Tensile testing at ambient

temperatures was performed on Zwick/Roell Z020 universal testing machine. The hardness of the alloys was

measured by the brinell method at a load of 613.0N. The corrosion test was worked on EC500 electrochemical

workstation in 3.5% NaCl solution at a sweep rate of 1 mv/s. The hydrogen evolution rate was made in 1500ml

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3.5% NaCl solution. The sample size of hydrogen evolution is about φ10×10mm. Minimum three specimens

were carried out for hydrogen evolution rate.

Results： The Mg12YZn phase, α-Mg and the Mg12(Zn, Nd) phase are observed in the Mg-Zn-Y-Nd alloy. The

microstructure transition is that disappearance of the lamellar Mg12YZn phase and formation of the skeletal net

Mg12Nd phase. The enthalpy of second phase of Mg96Zn1Y2Nd1 alloy is less than that of other alloy. Though the

existence of the Mg12ZnY phase and the Mg12(Zn, Nd) phase of Mg96Zn1Y2Nd1 alloy simultaneously decrease the

stability of second phase, the thermal stability of the Mg95ZnY2Nd2 alloy improves due to the volume fraction of

Mg12(Zn, Nd) phase.

The Nd also can improve the ultimate tensile strength (UTS) of the Mg-Zn-Y-Nd alloy. The UTS of the

Mg96ZnY2Nd1 alloy is 197MPa because the second phase of Mg96ZnY2Nd1 alloy is uniform distribution and small

grain size. Another reason may be that the formation of Mg12ZnY phase is precipitation on the surface of the

Mg12(Zn, Nd) phase in the Mg96Zn1Y2Nd1 alloy.

From the corrosion resistance test, the corrosion rate of Mg-Zn-Y-Nd alloy increases with the Nd addition before

20 hours by hydrogen evolution rate. Then, the corrosion rate of Mg96.5ZnY2Nd0.5 alloy is lower than that of other

alloys by hydrogen evolution rate. The dynamic potential polarization test is also found that the corrosion current

density of Mg96.5ZnY2Nd0.5 alloy is lower than that of other alloys. It means that the negative difference effect

occurs in the early stages of corrosion reaction in the Mg-Zn-Y-Nd alloy. The reason may be that an increase of

film-free areas and the formation of monovalent magnesium ion cause the increasing corrosion rates in the early

stages of corrosion reaction.

Conclusions (1) The Nd addition should promote the formation of Mg12(Zn, Nd) phase in Mg-Zn-Y-Nd alloy. The

existence of the Mg12ZnY phase and the Mg12(Zn, Nd) phase simultaneously decrease the stability of second

phase in Mg96ZnY2Nd1 alloy. The reason may be that atomic size mismatch decrease the melt temperature. The

stability of Mg95Zn1Y2Nd2 alloy is higher than that of the Mg97ZnY2 alloy because of the large volume fraction of

Mg12(Zn, Nd) phase

(2) The UTS of the Mg95ZnY2Nd2 alloy is higher 32MPa than that of the Mg97ZnY2 alloy. The reason may be that

the difference second phase. The UTS of the Mg96ZnY2Nd1 alloy is 197MPa. The second phase of the

Mg96ZnY2Nd1 alloy is the existence of Mg12Nd and Mg12ZnY phases.

(3) The negative difference effect occurs in the early stages of corrosion reaction. The corrosion rate is that the Nd

addition increases the corrosion rate in Mg-Zn-Y-Nd alloy in the 20 hours ago. After the 20 hours, the Nd addition

0.5at. % should decrease the corrosion rate.

Microstructure; Mechanical properties; Negative difference effect;

Effect of Heat Treatment on Microstructure of Near Alpha High Temperature Titanium Alloy

Tao Li, Lihua Chai, Zhilei Xiang, Ziyong Chen

Beijing University of Technology

The ingot of Ti-Al-Sn-Zr-Mo-Nb-W-Si-Er near alpha high temperature titanium alloy was prepared by induction

skull melting with a water cooled copper crucible. The pancake was obtained by forging with the basket weave

microstructure. The effect of heat treatment, such as solution and aging, on the microstructure and

phase composition for the near alpha high temperature titanium alloy was studied in this paper. Different methods,

such as OM, SEM and XRD, were applied to evaluate the microstructure and phase composition. The results show

that the content of primary alpha phase decreases with the increase of temperature during solution treatment in the

alpha-beta phase region. Moreover, the primary alpha phase has a tendency of spherical transformation. During

solution treatment above beta transformed temperature, the widmanstatten microstructure is achieved and the

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grain size increases. The increase of solution time has no obvious effects on the microstructure after one hour.

After aging treatment, the content and the size of secondary alpha phase increases.

near alpha high temperature titanium alloy; heat treatment; microstructure

Numerical and experimental study on the extrusion of magnesium tubeNon-ferrous metals and alloys (A);

Wrought (B); Extrusion (C)

Tao Lin1, Yun-teng Liu1,2, Ji-xue Zhou1,3, Yuan-sheng Yang4

1. Shandong Academy of Sciences Advanced Materials, Jinan 250014, China

2. Shandong Key Laboratory for High Strength Lightweight Metallic Materials (HLM)

3. Shandong Engineering Research Center for Lightweight Automobiles Magnesium Alloys

4. Institute of Metal Research Chinese Academy of Sciences, Shenyang 110016, China

In this paper, the thermomechanical behaviour of a magnesium alloy AZ31B during extrusion tube without weld

seams was study. Numerical simulation revealed that the strain rate is larger than 10.Based on the classical flow

stress and kinetics of dynamic recrystallization, a model was developed to determine flow stress of magnesium

alloy at hot deformation condition and high deformation rate. Experimental measurements of extrusion pressure

and extrudate temperature were found to be in agreement with the predicted values. It is thus the ratio of the

maximum normal pressure in the welding chamber to the flow

stress of the workpiece material on the welding plane that determines the weld seam quality.

Non-ferrous metals and alloys; Wrought; Extrusion

Microstructure characterization, texture evolution and mechanical properties of Nd:YAG laser welded

AZ31 magnesium alloy

Hongtao Liu1, Jixue Zhou1, Dongqing Zhao2, Yunteng Liu1, Di Zhang2, Yuansheng Yang3,1

1. Shandong Key Laboratory for High Strength Lightweight Metallic Materials, Advanced Materials Institute,

Shandong Academy of Sciences, Jinan 250014, China

2. Shandong Engineering Research Center for Lightweight Automobiles Magnesium Alloys, Advanced Materials

Institute, Shandong Academy of Sciences, Jinan 250014, China

3. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China

The Nd:YAG laser welding process of AZ31 alloys was performed by using the six-axis robot in this work.

Microstructure characterization and mechanical properties of AZ31 auto-welded joints were studied by using

optical microscopy (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and

mechanical test machines. Especially, texture evolution in the base metal (BM), heat affected zone (HAZ) and

fusion zone (FZ) was carried out by electron backscatter diffraction (EBSD). Accompanied with divorced eutectic

β-Mg17Al12 particles, laser welding process resulted in the formation of equiaxed dendrites in the FZ and

columnar dendrites near the FZ boundary. Dimple-like ductile fracture characteristics appeared in the

BM, nevertheless some cleavage-like flat facets together with dimples and river marking were observed in welded

joints.

Nd:YAG laser welding; AZ31 magnesium alloy; Microstructure characterizations; Texture evolution; EBSD;

Mechanical properties

Analysis on the microstructure and mechanical property of Mg-Sn-Al wrought magnesium alloys

Zhenghua Huang1, Nan Zhou1, Jing Xu1, Yangde Li2, Weirong Li2

70

1. Guangdong Institute of Materials and Processing, Guangdong Academy of Sciences, Guangzhou 510650,

China

2. DongGuan EONTEC Co. Ltd., DongGuan 523662, China

Microstructures and phase composition of as-cast samples, extruded rods and extruded plates of

Mg-3.52Sn-3.32Al and Mg-6.54Sn-4.78Al alloys were investigated by optical microscopy, scanning electron

microscopy and X-ray diffraction. Meanwhile, the tensile mechanical property was tested. The results show that

the as-cast microstructures of the two alloys consist of a-Mg matrix, Mg2Sn and few dispersed β-Mg17Al12 phases.

The two alloys exhibit the relatively excellent as-cast tensile mechanical property. After hot extrusion, the

microstructures of the rods and plates occur the obvious dynamic recrystallization. The average grain size only

reaches the range from 6 um to 8 um for the rods, and is slightly larger for the plates under the extruded and

transverse directions. Meanwhile, many fine micro-particles exist. The tensile mechanical property of the extruded

rods and plates is enhanced significantly. Mg-3.52Sn-3.32Al alloy extruded rod exhibits the better comprehensive

tensile mechanical property than AZ31B alloy, whose tensile strength, yield strength and elongation reach 295

MPa, 200 MPa and 21.5% at ambient temperature, respectively. Mg-6.54Sn-4.78Al alloy extruded rod exhibits

the equivalent comprehensive tensile mechanical property with ZK60 alloy, whose tensile strength, yield strength

and elongation reach 355 MPa, 275 MPa and 11.0% at ambient temperature, respectively. Tensile strength of the

two alloy extruded plates at ambient temperature reaches 270 MPa and the range from 295 MPa to 315 MPa,

respectively.

wrought magnesium alloy; Mg-Sn-Al alloy; microstructure; mechanical property

Effect of aluminum on microstructure and mechanical properties of as-cast magnesium-manganese alloys

Zhengwen Yu1,2,3, Aitao Tang3, Mingsong Wu1,2, Qian Wang1,2, Fangyuan Wang1,2, Bin Chen1,2, Jiejun He4,

Zhengyuan Gao5,6, Jianguo Liu2, Fusheng Pan3

1. School of Dentistry, Zunyi Medical University, Zunyi 563003, PR China;

2. Research Center for Medicine & Biology, Zunyi Medical University, Zunyi 563003, PR China;

3. College of Materials Science and Engineering, Chongqing University, Chongqing 400044, PR China;

4. College of Materials and Metallurgy, Guizhou Institute of Technology, Guiyang 550003, PR China;

5. School of Mechatronics and Automotive Engineering, Chongqing Jiaotong University, Chongqing 400074, PR

China;

6. Chongqing Academy of Metrology and Quality Inspection, Chongqing, 401121, PR China;

In this paper, the effect of aluminum on microstructure and mechanical properties of as-cast

magnesium-manganese alloy has been investigated by means of X-ray diffraction (XRD), optical microscope

(OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and thermodynamic

calculation. The results reveal that the formation of various Al-Mn intermetallic compounds is with the addition of

Al ranging from 0 to 9.0 wt. %. As a result, microstructure of AM11 alloy has been effectively refined due to the

formation of Al8Mn5 phase, and Al addition is explained as the main reason to refine the microstructure of AM91

alloy due to its higher grain growth restriction factor value of ~4.32. The tensile yield strength has been improved

steadily from 27.4 MPa to 122.9 MPa with an increase of Al addition, due to the combined effects of grain size

strengthening, solid solution strengthening and precipitation hardening behaviors.

Magnesium-manganese alloys; Aluminum; Microstructure; Mechanical properties; Precipitation hardening

Microstructure and mechanical properties of a WE91 alloy

71

Minglong Ma, Kui Zhang, Xinggang Li, Yongjun Li, Guoliang Shi, Jiawei Yuan

State Key Laboratory of Nonferrous Metals and Processes, General Research Institute for Nonferrous Metals

The microstructure and mechanical properties of Mg-9Y-1MM-0.6Zr (WE91) alloy were investigated through

optical microscopy, scanning electron

microscopy, X-ray diffraction, transmission electron microscopy, and mechanical property tests. Results showed

that the WE91 alloy cast was mainly composed of α-Mg matrix and eutectic structures. After homogenization was

completed, most of the eutectic structures of the alloy were dissolved except the Mg12(MM) phase. After extrusion

was performed, the alloy underwent dynamic recrystallization, and the grain size of the alloy decreased

significantly. The residual Mg12(MM) phase was distributed along the direction of extrusion. The reasonable

aging condition of the WE91 alloy was 225 °C × 28 h; under this condition, numerous long lens-shaped β′ phases

precipitated. After aging occurred, the alloy exhibited good resistance to high temperatures. The strength of the

alloy slightly reduced at temperatures below 250 °C; meanwhile, the strength of the alloy significantly reduced at

300 °C. As the testing temperature increased, the crack propagation changed from transgranular to intergranular.

The precipitated Mg-Y and Mg12(MM) phases, as well as the precipitate-free zone, could affect the final

properties of the WE91 alloy.

Rare earths magnesium alloy; Microstructure; Mechanical properties; Fracture behavior

Effect of the content of glycerophosphoric acid calcium salt on the properties of micro arc coatings on

Mg-8Li-2Ca

Wei Miao, Ruizhi Wu, Milin Zhang

Key Laboratory of Superlight Materials & Surface Technology, Ministry of Education, Harbin Engineering

University

Micro-arc oxidation (MAO) coatings were obtained on Mg-8Li-2Ca alloy in an alkaline Na3PO4-

glycerophosphoric acid calcium salt base solution. The surface and cross-sectional morphologies, elemental

compositions and phase structure of the resulting coatings were investigated by scanning electron microscopy

(SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The corrosion

behavior of the coatings was evaluated by potential dynamic polarization (PDP) curves and electrochemical

impedance spectroscopy (EIS) in SBF solution. The mechanical properties of the coatings were characterized with

microhardness test and friction and wear experiments. Results show that the MAO coating consists of MgO,

Ca2H2P3O4 and Ca5(OH)(PO4)3. With the increase of glycerophosphoric acid calcium salt content, the number of

the micro pores decreases and the size of the pores increases. The coating exhibits a more dense cross-sectional

morphology. The anticorrosion properties and mechanical properties increase first and then decrease.

Micro arc oxidation coatings; Glycerophosphoric acid calciumsalt; Anticorrosion properties; mechanical

properties

Effect of Nd content and heat treatment on microstructure and mechanical properties of Mg-Zn-Nd alloy

Shumin Xu, Xinying Teng, Jinyang Zhang, Xingjing Ge

School of Mterials Science and Engineering, University of Jinan, No. 336, West Road of Nan Xinzhuang, Jinnan

250022, People's Republic of China

Objective: In this paper, the microstructure and mechanical properties of the as-cast and heat treatment about

Mg-Zn-Nd alloy (which was designed for four groups and the Nd content were 1at.%, 2at.%, 3at.% and4at.%,

respectively.) were investigated.

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Methods: The alloy is manufactured by a conventional casting method, and then subjected to a heat treatment. The

microstructure was observed by scanning electron microscopeand X-ray diffractometer. The mechanical

performance was detected by electronic universal testing machine.

Results: The as-cast alloy is comprised of a-Mg matrix and Mg12Nd eutectic compounds. In as-cast, with the

increasing of Nd content, the grain size gradually decreases from 25.38μm to 9.82μm because the influence of

high temperature stable phase MgNd5 hided the grain growth during solidification. The hardness, ultimate tensile

strength and elongation at room temperature about the Mg94Zn2Nd4 alloy could be reached to 79.30HV,

219.07MPa and 5.11%, respectively. After the heat treatment craft, the Mg12Nd eutectic compounds dissolved

into the magnesium matrix and the grain size becomes a little lager than that of the as-cast. The hardness and

ultimate tensile strength was slightly declined by about 3.5%, and the elongation was obviously increased by

about 28.2%.

Conclusion: Therefore, adding a certain amount of Nd and an appropriate heat treatment process in this paper

could refined the grain size to some extent and then improve the mechanical properties of Mg-Zn-Nd alloy.

Mg-Zn-Nd alloy; Nd content; heat treatment; microstructure; mechanical properties

Effects of the Al-Ti-B-Sr master on the microstructure and mechanical properties of A356 alloy

Houliang Zhao1, Jianhua Wu2, Jixue Zhou2, Weihong Li2, Jinwei Wang3, Linlin Zhang3

1. Shandong Jianzhu University

2. Shandong Key Laboratory for High Strength Lightweight Metallic Materials (HLM), Advanced Materials

Institute，Shandong Academy of Sciences

3. Shandong Engineering Research Center for Lightweight Automobiles Magnesium Alloys, Advanced Materials

Institute，Shandong Academy of Sciences

Commercial A356 alloy was refined with a new Al-5Ti-B-10Sr master alloy, and the microstructure and

mechanical properties of the A356 alloy with different master alloy (0, 0.1, 0.3, 0.5 and 0.7 wt.%) were

investigated. The results show that the grain refining effect of as-cast A356 alloy is poor by the addition of 0.1 wt.%

master alloy, but when the level reaches 0.3 wt.% the grain can get a satisfactory refining effect, and the refining

effect becomes worse with the addition increasing, sequentially. Furthermore, an optimal combination of the

tensile strength (193 MPa) and the elongation (17.8%) of as-cast A356 alloy was achieved by the 0.3 wt.% master

alloy. Compared to the non-modified A356 alloy, the tensile strength and the elongation were improved by 10%

and 242%, respectively.

A356 alloy, Al-Ti-B-Sr, Microstructure, Mechanical properties

Creep behavior of Mg-Zn-Mn alloy with high thermal conductivity

jiawei yuan, kui Zhang, xinggang Li, yongjun Li, minglong Ma, guoliang Shi

General Research Institute for Nonferrous Metals

The effect of Zn content, extruded and heat treatment on the creep behavior of Mg–Zn-Mn alloy with high

thermal conductivity was investigated under the condition of temperature between 100 and 150℃ and applied

stress 50 MPa. The creep resistance of Mg-Zn-Mn alloys increases with increasing Zn concentration. The as-cast

Mg-5Zn-1Mn (wt. %) alloy exhibited the highest creep resistance and the as-extruded condition exhibited the

lowest creep resistance. Aging treatment (T5 and T6) can drastically improve the creep properties of

Mg-5Zn-1Mn, the minimum creep rate of the peak-aged (T6) alloy almost near that of the as-cast, which was

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almost two orders of magnitude lower than that of as-extrude alloy. It is found that lager grain size and

precipitation phases were beneficial for the improvement of creep resistance.

Mg-Zn-Mn alloy；Creep resistance

The microstructure evolution of Mg-4.5Zn-0.75Er alloy containing I-phase during compression

Cuicui Sun1,2, Ke Liu3, Wenbo Du3, Jixue Zhou1,2, Yuansheng Yang4

1. Shandong Key laboratory for High Strength Lightweight metallic Materials, Advanced Material Institute,

Shandong Academy of Science, Jinan, 250014, China

2. Shandong Engineering Research Center for Lightweight Automobiles Magnesium Alloys, Advanced Materials

Institute, Shandong Academy of Science, Jinan, 250014, China

3. College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China

4. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China

The microstructure evolution of the Mg-4.5Zn-0.75Er alloys containing quasicrystalline phase (I-phase) during

heat treatment and hot compression was investigated by means of optical microscopy (OM), scanning electron

microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that the

as-cast alloys mainly consisted of α-Mg matrix and I-phase. The I-phase with different morphologies could be

found at both matrix and interdentritic boundaries. The I-phase almost dissolved into the matrix at 460 °C,

meanwhile, some magnesium-rare earth phase (Mg-RE phase) was precipitated and the volume fraction increased

with the solid solution time prolonging. The true stress-strain curve obtained from the hot compression test

showed the flow stress first increased to a maximum and then decreased to a steady state. It indicated that the

dynamic competition between the working hardening and working softening during hot compression. Moreover,

the main deformation mechanism was twining at strain of 0.08 for the as-solution alloy, with the increment of

strain, dynamic recrystallization (DRX) grains appeared at original grains and twins boundaries. In addition, lots

of nano-scale I-phase which pined and hindered dislocation were precipitated within the matrix during hot

compression process.

Mg-4.5Zn-0.75Er, I-phase, microstructure evolution

Numerical and Experimental Studies of the Al/Mg Alloy Composite Plates by Explosive Welding

Tingting Zhang1,2, Wenxian Wang1,2

1. College of Materials Science and Engineering, Taiyuan University of Technology

2. Key Laboratory of Interface Science and Engineering in Advanced Materials

In this work, an excellent layer composite plate of 6061/AZ31B alloy was fabricated by explosive welding. A

finite difference engineering package with smoothed particle hydrodynamics method was used to model the

oblique impact of the flyer plate (Al alloy plate) on the base plate (Mg alloy plate). The microstructure evolution

along the interface and bonding strength of composite plate were investigated. The interface bonding was bound

to be a possible solid-state welding process. The effective plastic strain exceeds a minimum value, and the shear

stress was just the opposite sign in simulation where available bonding occurred. Wave formation appears to be

the result of variation in the velocity distribution on the interface and periodic disturbances of magnesium and

aluminum elements. Adiabatic shear bands were found on the magnesium alloy side adjacent to the interface. The

diffusion layer in the bonding interface was approximately 2.0 μm, and no intermetallic compounds were detected.

The results of nano-indenter testing showed the hardness values decreased with the increase of the distance from

the

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bonding interface. The optimized bonding interface shear strength can reach 201.2 MPa.

Al/Mg composite plate; Explosive welding; Simulation; Microstructure; Mechanical properties

Numerical Simulation of Superplastic Forming Limit of AZ31B Magnesium Alloy sheet

Meijuan Song1, Chuanhui Huang1, Min He1, Yi Xiang2, Yamei Wu2

1. Xuzhou institute of technology

2. Chongqing university of science and technology

Abstract:Numerical simulation of superplastic forming limit of AZ31B magnesium alloy sheet were investigated

in this paper. The damage evolution equation based on the law of the micro-damage evolution and statistical

mechanics was derived out, and damage characteristic parameters as well as the critical value of damage variable

were identified so as to provide a theoretical ground on which the plastic forming technology of magnesium alloy

sheet can be optimized. The theoretical prediction was done with the numerical simulation program, and its results

were verified by experiments. The forming limit curve of the theoretical prediction drawn by numerical simulation

establish the basic adaptation of the forming limit curve based on the experimental data.

AZ31B magnesium alloy; superplasticity; forming limit; damage

Study on the Change of Structure and Properties of Rolled Magnesium Alloy Thick Plate with Normal

Position

Weibo Zhu1, Aimin Jiang1, Qiu Jin2, Yufan Ding1

1. Chongqing Academy of Science and Technology

2. Southwest University

The purpose of the experiment is to study the relationship and principle between the mechanical properties of

rolled magnesium alloy sheet in the whole and normal positions.

The samples of this test are a group of tensile samples, which are processed from the whole and normal different

positions of rolled AZ31 magnesium alloy sheet. Microstructure and properties of rolled AZ31 magnesium alloy

sheet with the change of normal position，by electronic universal testing machine, ZEISS optical microscopy,

scanning electron microscopy.

The tensile test results show that the mechanical properties of the thickness of the second groups are closest to the

whole. It can be seen from the microstructure of the samples that a large number of tiny grains are distributed

around the larger grains. The majority of these grains are the equiaxed grains, and the twins almost disappear. As

can be seen from the tensile fracture, the tensile fracture surfaces of all samples have the dimple and tearing ridge.

The fracture mechanism is the two mixed fracture mechanism of ductile and brittle fracture.

Rolled AZ31 Magnesium Alloy Sheet;Normal Position;Mechanical Property;Microstructural

A high strength and toughness Mg–Y- Ni alloy with a long-period ordered phase

suqin Luo1,2, Aitao Tang2,1, Bin Jiang2,1, Weiwei Du1, Wenjun Liu1, Fusheng Pan1,2

1. Chongqing Research Center for Advanced Materials，Chongqing Academy of Science and Technology,

Chongqing 401123, China

2. National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400030,

China

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A Mg–5.08Y–3.54Ni (wt.%) alloy was prepared by casting, heat treating at 480 C for 10 h, extruding at 450 C.

Microstructure characterization revealed that this alloy consists of the fine-grained a-Mg matrix composed of long

period stacking ordered (LPSO) phase and a small amount of Mg2Ni precipitations. Tensile tests showed that the

yield and ultimate tensile strengths of this alloy can reach 401MPa and 317MPa at room temperature, while the

elongation of this alloy is 7.8%. The high volume fraction of LPSO phase in the fine-grained a-Mg grains and the

distributed Mg2Ni were responsible for the excellent strength, while large-angle deformation kinks observed in

LPSO was responsible for the excellent toughness observed for this alloy.

magnesium alloys; LPSO; deformation kinks

Effect of deformation induced precipitates in microstructural evolution during final thermo-mechanical

processing 7055 Al Alloy

Jinrong Zuo1, Longgang Hou1, Jintao Shi1, Hua Cui2, Linzhong Zhuang1, Jishan Zhang1

1. State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing

2. School of Materials Science and Engineering, University of Science and Technology Beijing

The 7xxx series Al alloys has been widely used in the aircraft, automotive, ship-building and nuclear industries

for the advantages of excellent combination of low density, high strength to weight ratio, good toughness, and

high corrosion resistance, etc. The dynamic aging process can obviously affect the matrix precipitation that occurs

concurrently with the evolution of the grain boundary precipitation in heat treatable Al alloys like 7xxx series.

This paper describes an optimization study on the production of 7055 sheets using a new final thermomechanical

treatment (NFTMT) that includes peak aging and a subsequent dynamic aging. The optimization was based on

nigh well-planned orthogonal experiments (OA9 matrix). Three main process conditions in the thermomechanical

treatment for obtaining the optimum synthetic properties of 7055 (i.e. preheating temperature, final rolling

temperature and deformation amount) were investigated. It was found that the order of significant factors for 7055

Al alloy is final rolling temperature > preheating temperature > deformation amount. Based on the results of the

range analysis and analysis of variance (ANOVA), the optimum synthetic properties of 7055 Al alloy was found

at the preheating temperature of 140oC, the final rolling temperature of 170oC, the deformation amount of 40%.

The yield stress and ultimate stress of 7055 Al alloy under optimal conditions reached 651.1 MPa and 659.7 MPa,

respectively. The properties of the electrochemical corrosion resistance, resistance to intergranular corrosion,

exfoliation corrosion resistance, etc., were determined and compared with the sheet produced by conventional

peak aging (T6: 120oC /24 h). The corresponding microstructural evolution is also investigated. It shows that, with

the introduction of dynamic aging, the grain boundary precipitates become discontinuously distributed gradually

without much coarsening of matrix precipitates, while the grain boundary precipitates are continuously distributed

after T6 peak aging. As a result, the NFTMT process under optimal conditions can improve the intergranular /

exfoliation corrosion resistances without sacrificing the strength compared to T6 temper. The corrosion trends

were confirmed by polarization curves. It indicated that the present NFTMT process as a good alternative can

efficiently produce high-strength Al alloy sheets with good corrosion resistance.

Al-Zn-Mg-Cu; Grain boundary precipitate; thermomechanical treatment; Intergranular corrosion; Exfoliation

corrosion; Mechanical property, Electrochemical corrosion

Burning products of TA15 titanium alloy by friction oxygen concentration method

Nan Sui, Guangbao Mi*, Mengqi Yan, Jingxia Cao, Xu Huang

Aviation Key Laboratory of Science and Technology on Advanced Titanium Alloys, Beijing Institute of

Aeronautical Materials, Beijing 100095, China

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Titanium fire is a typical catastrophic failure in the modern aero-engine. The microstructure characteristics,

element distribution law and microscopic formation mechanism of the burning products of TA15 titanium alloy

are investigated by friction oxygen concentration method (FOC), associated with in-situ observation, XRD, SEM

and EDS analyses, providing the thoughts to improve fireproof property. The results show that, when the friction

contact pressure Pfric is 0.20MPa and oxygen concentration of premixed air flow c0 is 60%, TA15 titanium alloy

produces violent sparks and presents dazzling white light during combustion. The generated products after

burning are mainly TiO2 and small amount of Al2O3 oxides. Four distinct zones form from the combustion surface

to the alloy matrix, and they are in the sequence of combustion zone, fusion zone, heat-affected zone and

transition zone. Further, combustion zone is composed of TiO2 and Al2O3 compounds, containing obvious cracks.

In the fusion zone, discontinuous oxygen-rich Al-based solid solution forms, and the elements distribution has

strong volatility. In the heat-affected zone, there are abundant of Ti-based solid solution and small amount of Al

and Mo-based solid solution. Transition zone is made of lamellar structure. Two technical approaches are given to

prevent oxygen diffusion inside the reaction zone and reaction-affected zone. On the one hand, the content of Al is

designed as the upper limit of alloy composition, on the other hand, fireproof coatings are deposited on the surface

of the alloy.

Friction oxygen concentration method; TA15 titanium alloy; Burning products; Microstructure; Titanium fire

Effects of extrusion ratio on microstructures and properties of Al-Cu-Mg-Ag-Ce-Er alloy wires

Yupeng Xu, Ze sheng Ji

School of Material Science & Engineering, Harbin University of Science and Technology

In order to define the effects of extrusion ratio on microstructures, properties and nucleation mechanism of

dynamic recrystallization of Al-Cu-Mg-Ag-Ce-Er alloy wires, Al-Cu-Mg-Ag-Ce-Er alloy wires with different

extrusion ratio (λ=12, 25, 50, 100) were produced by hot extrusion at 450ºC. Effects of extrusion ratio on

microstructures, tensile strength and elongation of Al-Cu-Mg-Ag-Ce-Er alloy wires were researched by means of

OM, SEM, TEM and mechanical test. The different mechanisms of dynamic recrystallization corresponded to

different extrusion ratio alloy wires were discussed. The results show that with the extrusion ratio increase, the

average grain size decreases from 83µm to 42µm, the broken level of Al2Cu, Al8Cu4Ce and Al8Cu4Er increases,

and the evenness of distribution about these second-phases in alloy wires increases. The tensile strength increases

from 366Mpa to 459Mpa with the increasing of extrusion ratio, and the elongation decreases first (λ=12, 25) and

then increase with the extrusion ratio increase (λ=50, 100). Dynamic recrystallization for Al-Cu-Mg-Ag-Ce-Er

alloy is occurring at different extrusion ratio alloy wires. With the increasing of extrusion ratio, the main

nucleation mechanism of dynamic recrystallization changes from the sub-grain coalescence at lower extrusion

ratio (λ=12, 25) to the acceleration of second-phases for nucleation at higher extrusion ratio (λ=50, 100).

extrusion ratio; Al-Cu-Mg-Ag-Ce-Er alloy; dynamic recrystallization; nucleation mechanism

Dynamic recrystallization behavior of a new high strength TB17 titanium alloy

Zhe Wang, Xinnan Wang, Liwei Zhu, Zhishou Zhu

Beijing Institute of Aeronautical Materials

The dynamic recrystallization (DRX) characterizes of a new high strength TB17 titanium alloy during isothermal

compression experiments has been investigated in this paper. The effect of temperature and height reduction on

the microstructure evolution and DRX mechanism were investigated using OM, TEM and EBSD. The results

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shows: in α/β phase field deformed, the dislocation stuck on interface of α/β phase lead to the DRX of

primary α phase. While in β phase field deformed, the dislocation stuck on the β grain boundary lead to the

DRX of β grain. The β grain refined from 200μm to 85μm for DRX. The increasing of strain promoted the

DRX of TB17 titanium alloy for dislocation multiplication. Few fine recrystallization β grain formed at high

strain rates for dislocation stuck but did not grown up. With the raise of deformation temperature, the volume

fraction of recrystallization β grain increased.

TB17 titanium alloy; Dynamic recrystallization; Dislocation evolution

Study on heat treatment process of welded plates of EW75 magnesium alloy

Yongjun Li1, Chunfang Lu1, Minglong Ma1, Guoliang Shi1, Jiawei Yuan1, Xinggang Li1, Kui Zhang1,

Xiaodao Liu2, ShengQing Wang2

1. State Key Laboratory of manufacturing and processing of non ferrous metals, General Research Institute for

Nonferrous Metals

2. Nanjing Yunhai Special Metals Limited Company

In this paper, microstructure and mechanical properties of welded plates of EW75 magnesium alloy under

different heat treatment conditions were studied. The results show that the eutectic microstructure along grain

boundaries of weld zone all could decompose when the welded plates of EW75 magnesium alloy were heat

treated at 480℃, 500℃ and 520℃ conditions. With increasing of solution temperature and solution time

prolonging, the eutectic microstructure along grain boundaries of weld zone were dissolved more fully. When the

welded plates of EW75 magnesium alloy were treated at mentioned above temperatures, the grain size of base

metal all increased dramatically during the initial solution treatment. The average grain size of base metal

increased from 13um to 50 ~ 60um just for half hour. With increasing of solution temperature and solution time

prolonging, the average grain size of base metal was continuously increased obviously to 80um. Compared with

the process of aging treatment after solution, directly aging treatment at 220℃ for 10h was more benefit to

maintaining the strength of the welded plates of EW75 magnesium alloy.

EW75 magnesium alloy; welding; heat treatment; microstructure and properties

Precipitation kinetics analysis of the cooling process followed the solid solution treatment of 7X50

aluminum alloy

Lei Kang, Yuanjun Cui, Gang Zhao, Ni Tian

Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials and

Engineering, Northeastern University, Shenyang 110819, China

Based on the TTP curves of isothermal treatment and the continuous cooling curves of end face spray quenching

with the Φ70 mm Jominy specimen of 7X50 aluminum alloy, distribution of the hardness along the thickness

direction of 7X50 alloy thick plates was analyzed and predicted by means of the theory of isothermal precipitation

kinetics and the method of quench factor analysis. The results show that during 7050 alloy isothermal holding at

200~400℃, the exponential n in its Johnson-Mehl-Avrami equation is close to 1, which indicates that the

nucleation process of precipitates is unchanged. In that equation the k value is 7.420E-03 at 350℃, which

indicates that the nucleation and growth rate of new precipitates are very fast. The distribution of hardness along

the axial direction of Φ70 mm Jominy specimen of 7B50 alloy is predicted by the quench factor analysis method

after the end face spray quenching. When the distance between the spray end face is less than 65 mm, the

deviation of the predicted hardness and the measured hardness is less than 5%. It can be known that the result of

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the prediction is of high precision. By the quench factor analysis method, it is feasible to predict the distribution of

hardness along the thickness direction in thick plates of 7X50 alloy after quenching and aging. When the quench

factor analysis method is extended to predict the actual spray quenching process of 7B50 alloy thick plates, the

average cooling rate in the quench sensitive temperature range is 21.6℃/s and the hardness is up to 98.5% of the

maximum hardness at the position of 15 mm from the surface of thick plates after quenching and aging.

7X50 aluminum alloy, Quench factor analysis method, Prediction properties of alloys, TTP

(Time-Temperature-Properties) curves, Continuous cooling curves

The effect of melt overheating treatment on the melt structure and solidified structures of Al75Bi9Sn16

immiscible alloy

Peng Jia1, Haoran Geng1,2, Yuyao Ma1, Jinyang Zhang1, Chen Wu1, Yijun Ding1, Min Zuo1, Rongxue Liu1

1. School of Materials Science and Engineering, University of Jinan, No. 336, West Road of Nan Xinzhuang,

Jinan 250022, Shandong, PR China.

2. Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials, University of

Jinan, No. 336, West Road of Nan Xinzhuang, Jinan 250022, Shandong, PR China.

Objective: The effect of melt overheating treatment (MOT) on solidified structures has been widely studied many

years, and it has been found that the structures and properties of some alloys could be obviously improved by such

proper treatment. However, there is little research on the impact of MOT on immiscible alloy. Therefore, in this

paper, Al75Bi9Sn16 monotectic alloy undergoing liquid phase separation process, in which no compound is

involved and there is tiny mutual solubility among three components at ambient temperature, was chosen as

research object to investigate the influence of MOT on the core-shell structure of immiscible alloy, and elucidate

the mechanism of MOT, and provide a beneficial guidance and reference for preparation of monotectic alloy

core-shell structure via liquid phase separation.

Methods: Firstly, pure aluminum (99.998 wt. %), pure bismuth ((99.998 wt. %)and pure tin (99.998 wt. %) were

melted in a high-purity alumina crucible under an argon atmosphere and overheated to 1150 K for 30 min (named

Sample A) and 1250 K for 30min (named Sample B) in a vacuum resistant furnace, to ensure sufficient mixing of

all components and prevent oxidation. Next, the alumina crucible was taken from the vacuum resistant furnace

and the melt was poured into the cylindrical steel mould as quickly as possible to avert the liquid phase separation

prior to casting. Finally, we can obtain the cylindrical samples of Al75Bi9Sn16 alloy with designed nominal

composition, 4 mm in diameter and 60 mm in length.

The cylinder disks were cut from the central cross-section of the casting samples to observe the vertical

morphology. The cut disks were mounted into phenolic plastics, ground and polished mechanically without etch

to examine their phase constitution, macroscopic morphologies and component using an X-Ray diffraction (XRD,

Bruker D8 Advance) with a Cu Kα irradiation and a field emission scanning electron microscope (FESEM, FEI

QUANTA FEG 250) coupled with an energy dispersive spectroscopy (EDS). Furthermore, the back scattered

electron was used as a physical signal, so that the morphologies and composition distribution of the alloys can be

observed distinctly. Phase transformation behaviors were studied by a differential scanning calorimetry (DSC,

Mettler-Toledo TGA/DSC 1/1600) at heating and cooling rates of 10 K/min under argon flow.

The temperature dependence of resistivity (ρ–T curves) of Al75Bi9Sn16 liquid alloy was measured by DC

four-probe method with current-reversal technique. The voltage drop and temperature were measured by the

Keithley 2182A nanovoltmeter and the constant current was provided by PF66 M constant current source. All

measurements were under the protection of high pure argon gas (99.999 wt. %).

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The time of the liquid phase separation t0, the solidification coefficient K, the temperature gradient in radial

direction G, solidification rates v, and the thermal Marangoni migration velocity VMt of Bi-Sn-rich phase droplets

during solidification process are calculated on the basis of Fourier’s law, heat energy conservation equation and

square radical sign law of solidification.

Results:(1) The parabola change in ρ–T curves of liquid Al75Bi9Sn16 immiscible alloy and the exothermic

process in the range from 1033 K to 876 K in the DSC curves, corresponding to the liquid phase separation

process, may be attributable to concentration fluctuations and the transform from microscopic heterogeneity to

macroscopic heterogeneity. Furthermore, compared with Al75Bi25 alloy, adding Sn element into Al–Bi

immiscible alloys can decrease the temperature of monotectic reaction TM, the liquidus temperature TL, and the

width of liquid miscibility gap W.

(2) The phase transformation behaviors of immiscible Al75Bi9Sn16 alloy is consistent with the microstructure and

analysis. What’s more, the cross-sectional structure changes from multi-cell structure to core-shell structure with

increasing overheating temperature.

(3) The melt overheating treatment of Al75Bi9Sn16 immiscible alloy will lead to the decrease of the solidification

coefficient K and solidification rates v, the increase of the temperature gradient in radial direction G, the thermal

Marangoni migration velocity VMt and the time of the liquid phase separation t0, and promote the formation of

core-shell structure.

Conclusions：The melt overheating treatment of Al75Bi9Sn16 immiscible alloy can promote the formation of

core-shell structure. This study provides a theoretical basis for melt overheating treatment of immiscible alloys, a

method for quantitative calculation of the dynamic characteristics of phase separation process and solidification

process, and some clues for the preparation of immiscible alloys with core–shell structure via liquid phase

separation. It is important to further explore some controllable methods to obtain the perfect core-shell structure in

the proper composition.

Al-based immiscible alloy; Liquid phase separation; Melt overheating treatment; Core-shell structure;

Heterogeneity of liquid alloy; Resistivity

High Strength Mg-Zn-Y Nanostructure Alloys Reinforced by Mg12ZnY and Mg3Zn3Y2 Phase

jian zhu1, Xiaohua Chen1, Lu Wang1, Williamyi Wang2, Zikui Liu2, Junxiu Liu3, Xidong Hui1

1. State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing

2. Department of Materials Science and Engineering, The Pennsylvania State University

3. Department of ENT, Peking University Third Hospital

Mg-Zn-Y alloys with atomic ratios of Y/Zn = 0.75 ~ 2 and compositions of Zn = 2 ~ 7 at.% and Y = 4 ~ 7 at.%

are prepared by rapidly solidified powder metallurgy. The atomized powders with Y/Zn atomic ratios larger than

1 contain α-Mg dendrite and interdendritic X-Mg12ZnY phase, but those with Y/Zn atomic ratios of 1 and 0.75

have network W-Mg3Zn3Y2 phase besides above two kinds of phases. After hot extrusion, nanometer cellar

structure is observed in a-Mg matrix; X-phase and W-phase are changed into acicular and granular shape,

respectively. The X-phase in extruded alloy is not a simple long-period stacking ordered (LPSO) structure, but

consists of 18R LPSO structure, 2H-Mg and stacking fault. These alloys exhibit excellent mechanical properties at

room and elevated temperature, for example, the tensile strength of as-extruded Mg86Zn7Y7 alloy reaches up to

541 MPa at room temperature and 297 MPa at 250 °C, respectively. The strengthening mechanisms of

Mg-Zn-Y alloys are attributed to the nanocrystalline strengthening of α -Mg matrix, the second-phase

strengthening of LPSO structure and the synergistic strengthening of X-phase and particulate W-phase.

Mg-Zn-Y alloy; Mg3Zn3Y2 phase; LPSO structure; Nanocrystalline strengthening; Mechanical properties

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Improvement of mechanical properties and in vitro degradation resistance of biodegradable

Mg-1.5Zn-0.6Zr-0.2Sc alloy by extrusion

Tao Li1,3,4, Hailong Zhang4, Shouqiu Tang1,2, Yuansheng Yang1,3, Jixue Zhou1,2, Xitao Wang5

1. Shandong Key Laboratory for High Strength Lightweight Metallic Materials, Advanced Materials Institute,

Shandong Academy of Sciences, Jinan 250014, China

2. Shandong Engineering Research Center for Lightweight Automobiles Magnesium Alloys, Advanced Materials

Institute, Shandong Academy of Sciences, Jinan 250014, China

3. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China

4. State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing,

Beijing 100083, China

5. Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing

100083, China

Magnesium alloys are considered as potential choice for the next generation of biodegradable implant materials.

However, their corrosion resistance and mechanical performance are still not much qualified despite a great deal

of effort has been made. In the present study, extrusion was performed on a novel biodegradable

Mg-1.5Zn-0.6Zr-0.2Sc alloy, and their microstructure, mechanical properties, and in vitro degradation behavior

were investigated. Microstructure observation showed that grain sizes were significantly refined after extrusion.

However, there existed some elongated grains along the extrusion direction. The strength, elongation, and

hardness of the alloy all improved after extrusion. The fracture mode transferred from quasi-cleavage fracture to

ductile and cleavage mixed fracture. The strengthening mechanism belongs to grain refining strengthening. The

cross section of the as-extruded alloy showed the lowest degradation rate compared with the longitudinal section

of the as-extruded alloy and the as-cast alloy. This can be explained by much refined grains, high microstructure

uniformity, and low dislocation density.

Magnesium alloy; Degradation; Extrusion; Mechanical properties

Effects of the Sc addition on microstructure and tensile properties of Mg-4Li-3Al-1Zn alloy

Jiayan Zuo, Ruizhi Wu, Milin Zhang

a Key Laboratory of Superlight Materials & Surface Technology, Ministry of Education, Harbin Engineering

University, Harbin 150001, P. R. China

Mg-4Li-3Al-1Zn alloys with different Sc additions were prepared with vacuum melting furnace under the ambient

of pure argon, and processed with extrusion deformation. The effects of scandium addition on the microstructure

and mechanical of the alloys have been investigated by X-ray diffraction, optical microscope, scanning electron

microscopy, energy dispersive X-ray spectroscopy and tensile properties testing. The results show that, after the

addition of Sc, the grains are refined and a new phase, Al3Sc, exists in the alloys. The tensile strength of the alloys

is improved because of the addition of Sc．The as-extruded Mg-4Li-3AI-1Zn-0.10Sc possesses the best tensile

properties. Partial dynamic recrystallization happens in the as-extruded alloys.

Mg-Li alloy; Sc Additions; hot extrusion; Microstructure; tensile properties

Effect of cooling rates on solidification and microstructure of Mg-Zn-Nd quasicrystal alloy

Xingjing Ge, Xinying Teng, Shumin Xu, Jinyang Zhang

School of Materials Science and Engineering, University of Jinan

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The influence of cooling rates on the solidification and microstructure of rapidly solidified quasicrystal alloys

with a nominal compositions of Mg70.8Zn28Nd1.2(at.%) prepared by conventional casting and melt spinning

method was investigated. The microstructure, phase constitution, phase transition, and phase structure of the

alloys were examined by means of scanning electron microscopy, x-ray diffraction, energy dispersive

spectrometer, differential scanning calorimetry. The experimental results show that the as-cast Mg70.8Zn28Nd1.2

alloy phase composition includes the quasicrystal I-phase and Mg7Zn3 phase, and I-phase is spherical uniform

distribution. For rapid solidification alloy, when the speed is not higher than 400 r/min, the microstructure

includes I-phase, Mg7Zn3 phase and α-Mg phase. When the speed continues to rise to no more than 2000r/min,

the Mg7Zn3 phase disappeared, only quasicrystal and α-Mg phase. With the increase of rotational speed, the

grain size decreases obviously, and there is a large number of microcrystals in microstructure. When the speed

reaches more than 2500 r/min, there may be amorphous phase in the alloy organization. Differential thermal

analysis shows that quasicrystal can be existed at about 340℃.

Mg-Zn-Nd quasicrystal; cooling rate; microcrystal; amorphous

Deformation feature of constituent phases in two-phase titanium alloys under tensile loading

Zhe ji, Yanqing Wang, Yinghuai Qiang

China University of Mining and Technology

Deformation feature of constituent phases has a significantly effect on strength and ductility of two-phase titanium

alloy. In this paper, two-phase titanium alloy with various microstructures varying in thickness of secondary α

plates but with the same primary α volume fraction (~50%) was produced by different heat treatment produces.

The deformation features and fracture mechanisms of constituent phases were investigate under tensile conditions

based on microstructure observations using scanning electron microscopy and compared to a reference material

with primary equiaxed α volume fraction of 16%. When primary α volume fraction is about 50%, elongation

along the tensile direction is the main deformation mode of equiaxed α and kinking is the dominated

deformation mode of α plates. The degree of α plates kinking increases with their thickness, leading to the

increase of the elongation of alloy. Although the thickness of secondary α plates is different, the micro-crack

mainly formed on the boundary of equiaxed α and propagated along α plates or by cutting α plates, leading

to the fracture of the alloy. When primary α volume fraction is 16%, equiaxed α slightly elongated but α

plates significantly kinked. The α plates become the main deformation phase and enhance the strength of the

alloy. The severe kinking of α plates lends to micro-void nucleated at the junction of different α colonies in

addition to the boundary of equiaxed α and decreases the elongation of the alloy.

Titanium alloy, constituent phases, Deformation, Mechanical property.

Effect of tungsten doping on phase transformation and hardness of Ti-22Al-25Nb alloy by powder

metallurgy

Qi Cai, Junpeng Yang, Yongchang Liu, Chong Li, Liming Yu, Huijun Li

State Key Lab of Hydraulic Engineering Simulation and Safety, School of Materials Science & Engineering,

Tianjin University, Tianjin 300072, P R China

The Ti-22Al-25Nb-xW alloys (x = 1.5, 2.5, and 3) were synthesized from the commercial Ti-22Al-25Nb powder

by solid-state sintering. The W doping postponed the phase transformation temperature from α2+B2+O to α

2+B2 phase field range, since the W element initially accumulated at the interface of the particles, and the

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concentration gradient from the interface to the inner grains indicated the formation of W solution within the

Ti2AlNb phase. Although the W solution hardly affected the phase composition of the alloys, it refined the

O-phase Widmanstatten precipitates. Due to such refinement, the hardness of the Ti-22Al-25Nb-xW was

improved in contrast with the original Ti-22Al-25Nb powder. However, the hardness decreased slightly with the

increasing W content. Furthermore, the Ti-22Al-25Nb-1.5W alloys were solution treated at 900 oC-1100 oC for 12

h followed by furnace cooling, and the optimal B2+O hybrid microstructure was realized.

Ti2AlNb; Tungsten doping; Powder metallurgy; Microstructure; Hardness.

Microstructure evolution and mechanical properties of AZ61 Mg alloy processed by two-pass friction stir

processing

Xicai Luo, Datong Zhang, Wen Zhang, Cheng Qiu

National Engineering Research Center Of Near-net shape Forming for Metallic Materials, South China University

of Technology, Guangzhou 510640, PR China

Friction stir processing (FSP) has been considered as a promising technique for grain refinement. In this study,

two-pass FSP was conducted under water to enhance the cooling rate during processing, and a fine-grained AZ61

magnesium alloy was prepared through this method. Compared with one-pass FSP, microstructure of the two-pass

FSP magnesium alloy is more homogeneous and finer, with an average grain size of 1.8 mm. Both the

tensile strength and ductility of the two-pass FSP specimen are improved due to grain refinement. A tensile

elongation of 31.8% was achieved in the two-pass FSP specimen. Microstructure evolution mechanism during the

processing was discussed based on the microstructure examination.

AZ61 Magnesium alloys; Friction stir processing; Microstructure; Mechanical property

Effects and mechanisms of grain refinement in aluminum alloys by a melting control technique

Xueyi Fan1,2, Yanqing Su2, Runzhou Hong1, Liang Wang2, Yongjiang Zhou1, Liangshun Luo2

1. Beijing Institute of Aeronautical Materials

2. Harbin Institute of Technology

This article further investigates the feasibility and the validity of grain refining by a melting control technique.

Using Al-Cu% and Al-Si% alloys to carry out the sand mold casting experiments, different alloy melt treatment

techniques are adopted in the casting experiments for grain refining. One is the direct-pouring after remelting, the

pouring temperature of which is 30℃ above the alloy liquidus-(RP). Another is high temperature melt-holding

prior to the pouring, in which the holding-temperature is 150℃ above the alloy liquidus for 1h, and then pouring

at the same temperature as that in the former treatment-(HP). To evaluate the sensitivity of grain refining to

cooling rates, step-castings in sand molds with helps of chill irons and thermal insulation materials to make as

large difference in cooling rates in the same casting as possible. In addition, to further confirm the

"dendrite-melting-fragment" mechanism, the technique of small block quick-Melting of the same compositions

shortly prior to pouring is also tested. Macrostructure examinations on sections of the tested castings are

conducted to evaluate the effectiveness of the present grain-refining method.

Grain refining, Melting control, Microstructure, Secondary dendrite arm spacing, Mechanical properties

Microstructure and Mechanical Properties of ZK60 Magnesium Alloy Prepared by Multi-Pass Friction Stir

Processing

Jun Lin, Datong Zhang, Wen Zhang, Cheng Qiu

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National Engineering Research Center of Near-Net-Shape Forming for Metallic Materials，School of Mechanical

and Automotive Engineering, South China University of Technology

Friction stir processing (FSP) is a novel severe plastic deformation technique developed in recent years to produce

fine-grained structural materials. In this paper, the microstructure and mechanical properties of ZK60 magnesium

alloy prepared by the single-pass and two-pass FSP were studied. The first-pass was subjected with

800r/min-100mm/min and the second-pass was subjected with 600r/min-100mm/min. The results show that the

coarse MgZn2 phase was dissolved into magnesium matrix and the α-Mg grains were remarkably refined in stir

zone after FSP. The average grain sizes of the single-pass and two-pass FSP alloys were 6.8μm and 6.0μm

respectively. The microhardnesses of the specimens were 70.1HV and 65.1HV, the ultimate tensile strengths were

276MPa and 255MPa, and the elongations were 31.6% and 42.5%, respectively. Through increasing the

processing pass, the microstructure becomes finer and the second phase is dissolved more thoroughly. The

combined effect of grain refinement and second phase dissolved was responsible for the change of mechanical

properties.

ZK60 magnesium alloy, Friction stir processing, Microstructure, Mechanical properties

Study on microstructure and hardness of as-cast TiAl-6Nb alloy with different Al content

Huimin Yang1,1, Liangshun Luo2,2, Chunyu Qiao1,2, Fangzheng Duan1,2, Chunyan Wang1,2, Chuang Yang1,2

1. Heilongjiang Institute of Technology

2. Harbin Institute of Technology

The effect of Al contents on the microstructure and hardness of as-cast TiAl-6Nb alloys was investigated by

optical microscope (OM), scanning electron microscope (SEM) and Rockwell hardness tester. The button ingots

of Ti-xAl-6Nb alloys were obtained using a non-consumable electric arc melting furnace. The results show that

the structures of Ti-xAl-6Nb alloys are the type columnar structure under the solidification condition. To compare

with TiAl binary alloys, Nb additions enlarge the beta phase solidification region. The critical value of the full

beta solidification region is 50 at.% Al in Ti-xAl-6Nb ternary alloys, that is to say, the primary solidification of

Ti-xAl-6Nb ternary alloys is the beta phase when Al contents less than 50 at.%. According to the SEM images of

Ti-xAl-6Nb ternary alloys, Nb elements were segregated in dendritic crystal, this is to say, B2 phases exist in

dendrite. As displayed by the hardness analysis, the hardness fitting curve of Ti-xAl-6Nb ternary alloys firstly

decreased and then increased.

TiAl alloy; Al element; Microstructure evolution; Hardness; Alloying method

Corrosion of Mg–5Li–1Al , Mg–9Li–1Al and Mg–14Li–1Al alloys in NaCl solution

qing xiang, bin jiang, ma shaoxing, pan fushegn

College of Material Science and Engineering, Chongqing University

Mg–5Li–1Al, Mg–9Li–1Al and Mg–14Li–1Al alloys were prepared by melting and casting method. Their

corrosion behavior in NaCl solution with different Cl- concentrations was investigated by electrochemical tests,

and the microstructures before and after corrosion were also examined by OM and SEM. The results showed

that Li content and Cl- concentration have important influence on the corrosion on these three alloys. Among these

alloys, Mg–9Li–1Al alloy possessed the highest electrochemical activity, which is attributed to its dual phase

microstructure . Corrosion of these Mg–Li alloys increased with the increase of Cl- concentration. The main

corrosion type was pitting corrosion.

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Mg-Li alloy; NaCl; corrosion; microstructure.

Constitutive equation and dynamic softening behavior of 7A55 aluminum alloy during compression at

elevated temperature

Di Feng1, Xinming Zhang2, Shengdan Liu2

1. Jiangsu University of Science and Technology

2. Central South University

The hot deformation behaviors of 7A55 aluminum alloy were investigated by compression tests at temperatures

ranging from 270℃ to 450℃ and strain rate ranging from 0.1s-1 to 25s-1 . Results show that the flow stress

increases with increasing strain rate and decreasing temperature. A two-stage constitutive equation was

established and the hot deformation activation energy was 140 kJ/mol. EBSD observations show that, fine and

equiaxed grains with the misorientation angle above 15° nucleate at the initial grain boundaries under high

temperature and low strain rate conditions. Combining with the analysis for efficiency of power dissipation based

on processing map, it is concluded that the softening mechanism of 7A55 aluminum alloy is dynamic

recovery(DRV), together with a partial dynamic recrystallization(DRX). The nucleation mechanism of DRX

could be explained by the strain induced grain boundary migration(SIBM). The optimum hot deformation

parameters were determined to be at the temperature range of 420℃～450℃ and strain rate range of 0.1s-1 ～

0.3s-1 .

7A55 aluminum alloy; Hot deformation; Dynamic softening; Processing map

Effects of cell structure on the mechanical properties of aluminium foams produced using powder pack roll

melting

yaoqi Wang1,2,3, Xueping Ren4, Daniel Balint5, Hongliang Hou1,2,3, Yanling Zhang1,2,3, Junyi Lee5

1. Beijing Aeronautical Manufacturing Technology Research Institute, Beijing 100024, China

2. Beijing Key Laboratory of Digital Plasticity Forming Technology and Equipment, Beijing 100024, China

3. Aeronautical Key Laboratory for Plastic Forming Technologies, Beijing 100024, China

4. School of Materials Science and Engineering, University of Science and Technology of Beijing, Beijing

100083, China

5. Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, UK

Aluminium foams with relative densities ranging from 0.17-0.52 were prepared by the powder pack roll melting

process using TiH2 as the foaming agent. The cell structure of aluminium foam was recorded and analysed

quantitatively in terms of cell size distribution. Uniaxial compression tests were carried at 0.01mm/s to investigate

the effects of relative density on the mechanical properties of the aluminium foams. It is found that the cell size

distribution of aluminium foams varies for different relative densities, and becomes wider when the foaming time

increases. The Young’s modulus and yield strength increase non-linearly with increasing relative density. The

deformation of aluminium foam initiates from the

defect bands consisting of incomplete cell walls and is dominated by the bending of cell edges. The energy

absorption up to densification strain of aluminium foams with the relative density of 0.34 reaches a maximum of

1.41MJ/m3.

Aluminium foam; Cell structure; Young’s modulus; Yield strength; Energy absorption.

Effects of Sn on the microstructure and mechanical properties in Mg alloy sheets processed by extrusion

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qingshan yang1,2, qingwei dai1, zujian yu1, wenjun liu2

1. Chongqing University of Science & Technology

2. Chongqing Academy of Science and Technology

The microstructure and mechanical responses of the AZ31 with addition of 1.8% Sn alloys have been studied and

compared. Mg alloy sheets were prepared with metal model casting method and subsequently processes by

conventional extrusion (CE) and differential speed extrusion (DSE). Mg alloys were hot extruded at 400oC with

the extrusion ratio of 101:1. The microstructure of mg alloy sheets was examined by optical microscopy (OM) and

scanning electron microscope (SEM). The results indicated that the grains were dynamically recrystallized after

the extrusion process. Moreover, DSE process dramatically enhances the room temperature ductility of the

extruded sheets. It was also presented that the mg alloy processed by DSE exhibits a classical dimple structure as

a result of slip accumulation and ductile tear.

Mg alloy; Microstructure; Mechanical properties; Extrusion.

Effects of misch-metal addition on microstructure and mechanical properties of as-cast Mg–7Al–3Sn

based alloy

guojun liu, jian rong, huiyuan wang

School of Materials Science and Engineering, Nanling Campus, Jilin University, No. 5988 Renmin Street,

Changchun 130025, PR China

Effects of minor misch-metal(MM) addition (0.2, 0.5, 1.0 and 1.0 mass %) on microstructure and mechanical

properties of the as-cast Mg–7Al–3Sn based alloy system are investigated by XRD, SEM and mechanical testing.

With the misch-metal addition of 0.5 % or higher, the alloys are composed of a-Mg, Mg2Sn, Al11Ce3 and

Mg17Al12 phases. The addition of MM can effectively refine the grain-size and dendrites compared to the relative

weak refinement of the compounds at the grain boundaries. The as-cast alloy with 1.0 % MM addition exhibits the

best mechanical properties at ambient temperature with the ultimate tensile strength and elongation of 239 MPa

and 13.2% respectively. However, excessive MM addition leads to the decreasing of strength and plasticity due to

the coarse intermetallic compound along at the grain boundarie

s. In addition, the mechanical properties at 175℃ and the corresponding fractographic analysis also have been

discussed.

Sn, Mg-Al-Sn alloys, mechanical properties, refine, misch-metal

The influence of oxide impurities on microstructure and thermals shock resistance of YSZ coatings

Yudao Wei1,2, Yueguang Yu1,2, Xiaojuan Ji1,2, Haoran Peng1,2, Kang Yuan1,2

1. Beijing General Research Institute of Mining and Metallugy

2. Beijing Engineering Technology Research Center of Surface Strengthening and

Repairing of Industry Parts

The main target of this study is to research the impact of impurities on microstructure and thermal shock

resistance of YSZ thermal barrier coatings. In this study, ZrO2-7.5wt%Y2O3(7.5YSZ) coatings of 5 spices of

compositions (4 with 1 type of impurity which were Al2O3, Fe2O3, SiO2 and TiO2 and 1 with none) were

manufactured by atmosphere plasma spray (APS) process. Thermal shock test was applied in these TBCs at 1100 ℃

and samples were quenched in cold water of temperature of 20-25℃. Microstructures evolution and phase

analysis were utilized before and after the thermal cycling test by scanning electron microscope(SEM) and X-ray

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diffractometer(XRD), separately. The results showed that thermal cycling lifetime of YSZ TBCs doped with

impurities was obviously harmed compared to that of high-purity TBCs. Additionally, differences in

microstructures and phase of YSZ TBCs of different compositions were ascertained and elements status was

tested by phase analysis technique.

high-purity TBCs, oxide impurities, microstructure, thermal shock resistance.