evirgen 1 , i. karaman 1 , r. santamarta 2 , j. pons 2

TAMU-UIB collaboration: TAMU-UIB collaboration:

characterization of Ni-Ti-Zr and Ni-Ti-Hf characterization of Ni-Ti-Zr and Ni-Ti-Hf

high temperature shape memory alloyshigh temperature shape memory alloys

TAMU-UIB collaboration: TAMU-UIB collaboration:

characterization of Ni-Ti-Zr and Ni-Ti-Hf characterization of Ni-Ti-Zr and Ni-Ti-Hf

high temperature shape memory alloyshigh temperature shape memory alloys

A. Evirgen1, I. Karaman1, R. Santamarta2, J. Pons2

1. Dept. of Mechanical Eng., Texas A&M University, TX, USA

2. Dept. of Physics, Univ. Balearic Islands, Palma de Mallorca, Spain

[email protected]

Activity in the framework of IIMEC in 2011Activity in the framework of IIMEC in 2011Activity in the framework of IIMEC in 2011Activity in the framework of IIMEC in 2011

PhD Student Exchange Activity: TAMU – UIB

Summer research stay of ALPER EVIRGEN (I. Karaman’s PhD

student) in UIB. July 2011 Financed by IIMEC

Research topic:

Study of (Ni-rich) Ni-Ti-Zr and Ni-Ti-Hf HTSMAs

[email protected]


PhD Student Exchange Activity: TAMU – UIB

Summer research stay of ALPER EVIRGEN (I. Karaman’s PhD

student) in UIB. July 2011 Financed by IIMEC

Research topic:

Study of (Ni-rich) Ni-Ti-Zr and Ni-Ti-Hf HTSMAs

NiTi: TM ~ 80ºC Increase of Ni content → TM drops

Substitution of Ti by Hf or Zr raises TM (Ti+Hf/Zr)-rich ternary alloys

Recently, study of Ni-rich ternary alloys

High industrial interest (automotive, aerospace, …)

[email protected]


[email protected]

MaterialsMaterialsMaterialsMaterials

Materials: Selected in TAMU

Ni50.3Ti34.7Zr15 15Zr (at%)

Ni50.3Ti29.7Zr20 20Zr

Ni50.3Ti34.7Hf15 15Hf

Hot extruded (900ºC)

Solution Heat Treatment: 900oC, 1h + WQ (SHT)

[email protected]

Collaboration planCollaboration planCollaboration planCollaboration plan

“Macroscopic” characterization of

functional properties

DSC

Thermal cycling under stress

Thermal treatments to

improve functional properties

Alper’s PhD

Microstructural characterization

TEM, HRTEM

EDX

Most of observations

performed during Alper’s stay

Afterwards: Analysis of results

[email protected]

General ResultsGeneral ResultsGeneral ResultsGeneral Results

VERY FRUITFUL ACTIVITY:

Education:

Intense immersion in practical TEM/HRTEM work

(preparation of samples and observations)

Personal life:

Stay in a country with different culture

Collaboration:

Strong impulse to TAMU-UIB collaboration

Scientific:

Good results suitable for several publications

[email protected]

Scientific ResultsScientific ResultsScientific ResultsScientific Results

As extruded and Solution Heat Treated state

Low TM temperatures and poor reproducibility

Thermal treatments to improve the alloy

performance

20Zr

15Hf

[email protected]


20Zr DSC results

[email protected]


15Hf DSC results

[email protected]


20Zr Furnace cooling from 700ºC to 100ºC in 48h

[email protected]


15Hf SHAPE MEMORY EFFECT

10h at 550ºC

~ 2.5%

[email protected]


Microstructural observations in aged samples

Precipitation of a new phase

Ni-rich NiTi Ni4Ti3 or Ni3Ti Not in ternary alloys

[email protected]

15Zr 200h at 500ºC Austenite at RT

Lenticular precipitates in austenitic matrix. ~ 20 nm


TEM HRTEM

[email protected]

The precipitates show an enhanced contrast every three 011 planes and extra spots in the diffraction patterns. They are fully coherent with austenitic matrix.


15Zr 200h at 500ºC Austenite at RT

[email protected]

15Hf 10h at 450ºC Austenite at RT

Nanometric precipitates (~5 nm)


[email protected]

20Zr 48h at 500ºC


15Hf 3h at 500ºC

Precipitates in martensite

[email protected]

20Zr 700ºC-100ºC FC

Long precipitates O(100 nm)


[email protected]

EDX Microanalysis


15Hf 10h at 600ºC

20Zr 700ºC-100ºC FC

at% Ni Ti Hf Precipitates 52.5 21.2 26.3 Matrix 49.2 34.0 16.8

at% Ni Ti Zr Precipitates 52.6 18.8 28.6 Matrix 49.6 30.8 19.6

Precipitates are richer in Hf/Zr and poorer in Ti, and a bit richer in Ni.

[email protected]

Twinning modes of B19’ martensite in samples with precipitates


[email protected]

Twinning modes of B19’ martensite in samples with precipitates


(011)B19’ Type I twinning Twin plane || intervariant boundary

(001)B19’ compound twinning (internal twins - LIS)

Same twinning modes and boundaries as reported in literature for Ni-Ti-Hf alloys

{111} and {113}-type intervariant boundaries

[email protected]

Intervariant boundaries


{111} or {113}-type boundaries quite irregular

(011)

Perfect (011) boundaries

|| twin plane

[email protected]

Structural model of the precipitate new phase


[email protected]

Benefits received from IIMECBenefits received from IIMECBenefits received from IIMECBenefits received from IIMEC

Benefits in Alper’s education and personal life

The summer stay provided a strong impulse to TAMU-UIB

collaboration

Several good publications envisaged

Creation of a good scientific common background for possible

future applications of research projects in International

Programs (NSF, EU, …)

[email protected]

Thanks for your attention!!!Thanks for your attention!!!Thanks for your attention!!!Thanks for your attention!!!

[email protected]

[email protected]


15Hf SHAPE MEMORY EFFECT

SHT

~ 3.5%

[email protected]


20Zr Af temperature vs ageing time

[email protected]


15Hf Af temperature vs ageing time

evirgen 1 , i. karaman 1 , r. santamarta 2 , j. pons 2

Documents