V.S.V.S. MoxsonMoxson (1)(1),Vlad A.,Vlad A. DuzDuz (1)(1), , Jane W. Adams Jane W. Adams (2)(2), Walter N. Roy , Walter N. Roy (2)(2)

(1) ADMA Products. Inc, 1890 Georgetown Road, Hudson, Ohio 44236, USA. US

(2) Army Research Laboratory, Weapons & Materials ResearchDirectorate, Aberdeen Proving Ground, Maryland 21005, USA

Direct Powder Rolling Process

Cooperative Agreement W911NF-05-2-000between US Army Research Laboratory and

ADMA Products, Inc.

Attractive Features of Direct Powder Rolling

1. Low Capital Cost compared to traditional melting, forging, etc.

2. Fewer operating steps compared with melting, forging, etc.

3. Availability of low cost raw materials

4. Precision control of composition and ability to use high purity metals

5. Applicable to composite type mixtures or immiscible components which currently cannot be produced by the conventional methods

6. Absence of texture and uniformity of microstructures and properties in longitudinal and transverse directions

7. Adaptability and versatility, including ability to roll multilayerstructures

Summary of Emerging Reduction Technologies

Name / Organization Process Product(s) FFC / Cambridge Univ. /

Quinetiq / TIMET Electrolytic reduction of partially sintered TiO2 electrode in molten CaCl2

Powder Block

MER Corp. Anode reduction of TiO2, transport through mixed halide electrolyte and deposition on cathode

Powder, Flake or Solid Slab

SRI International Fluidized bed reduction of Ti halide Powder, Granule BHP Billiton No details available NA

Idaho Titanium Technologies

Hydrogen reduction of TiCl4 plasma Powder

GTT s.r.l. (Ginatta) Electrolytic reduction of TiCl4 vapor dissolved in molten electrolyte

Liquid Ti, either tapped or solidified as slab

OS (Ono / Suzuki; Kyoto Univ.)

Calciothermic reduction of TiO2 Powder / sponge

Millenium Chemical No details available Powder MIR Chem I2 reduction of TiO2 in “shaking reactor” Particles

CSIR (S. Africa) H2 reduction of TiCl4 Sponge Quebec Fe & Ti (Rio

Tinto) Electrolytic reduction of Ti slag Ti Liquid

EMR / MSE (Univ. of Tokyo)

Electrolytic cell between TiO2 and liquid Ca alloy reduces TiO2

Highly porous Ti powder compact

Preform Reduction Reduction of TiO2 reduction by Ca Ti powder compact Vartech Gaseous reduction of TiCl4 vapor Powder

Idaho Research Foundation

Mechanochemical Reduction of liquid TiCl4 Powder

RMI Sodium reduced Ti sponge fines Powder Armstrong / International

Ti Powder Liquid Na reduction of TiCl4 vapor Powder

Domestic Powder “D” No details available Powder Powder “K” Innovative Kroll Process Powder Powder “U” US Patent No. 6,638,336 B1 Powder

Comparison of the conventional sheet process with the direct powder

rolling process for Ti-6Al-4V alloyConventional

INGOT

FINISHED SHEET

Direct Powder RollingElementalTi Powder

AlloyingPowdersBLEND

FINISHED SHEET

POWDER ROLLING

RE-ROLL

SINTER

ANNEAL

FORGING

ANNEAL

ROLL

ANNEAL

RE-ROLL

ANNEALETC.

ETC.

Direct powder rolling

Molybdenum plate

Ti alloy powder

Saw cut

Vacuum furnace

Ti alloy plateSintering

Powder rolling mill

Re-rolling mill

Re-rollingCompacted strip

Estimated cost = Powder cost + $2.0/lb

C.P. Ti, Ti-6Al-4V, and TiAl Plates Produced by Direct Powder Rolling + Sintering

• C.P. Ti powder;

• Ti-6Al-4V produced by blending of C.P. Ti powder with 10% by weight 60%Al/40%V master alloy;

• TiAl produced by blending of C.P.Ti powder with elemental powders;

Various thicknesses (0.020”-0.100”) and densities (50-99+%) single layer C.P. Titanium, Ti-6Al-4V, TiAl and composite Ti/Ti-6Al-4V/Ti and Ti-6Al-4V/TiAl/Ti-6Al-4V strips were produced by Direct Powder Rolling/Sintering.

Selection of Low Cost Titanium Powder Sources

• Sodium reduced Ti powder (Domestic Sources: RMI, Honeywell – ALTA Group)

• Powder “A” (Domestic Ti powder)

• Powder “D” (Domestic Ti powder)

• Powder “K” (Innovative Kroll process)

• Powder “U” (Modified magnesium reduced process, /US Patent No. 6,638,336 B1 )

Particle size of these powders was under 150 microns.

Chemical Composition of C.P.Ti Powder Used for Direct Powder Rolling

Powder Al C Cl Fe H2 Mg N Na O2 Ti Sodium reduced

<0.05 0.122 0.21 <0.05 0.096 <0.10 0.07 0.12 0.177 Bal.

Innovative Kroll

- 0.03 0.08 0.10 - 0.23 0.01 - 0.27 Bal.

Modified Mg

reduced

- 0.006 0.11 0.06 3.10 0.74 0.024 - 0.15 Bal.

Domestic “A”

<0.001

0.005 0.003 <0.001 0.005 0.019 0.009 0.055 0.15 Bal.

Domestic “D”

0.01 0.012 0.018 0.037 0.03 - 0.023 0.12 0.188 Bal.

Chemical Composition of BE Ti-6Al-4V Powder Used for

Direct Powder Rolling Other3

Class Al V C O N H1 Fe Ti Each Total Sodium reduced

6.00* 4.00* 0.0153 0.10 0.0041 0.0110 0.0036 Rem2 Cl 0.20 Na 0.13

0.40 max

“A” 6.00* 4.00* 0.0052 0.15 0.0086 0.005 0.001 Rem2 Cl 0.0027 Mg 0.019 Na 0.055

0.40 max

“D”* 6.00* 4.00* 0.021 0.123 0.11 0.018 0.006 Rem2 Cl 0.023 Na 0.11

0.40 max

“K”* 6.00* 4.00* 0.03 0.27 0.01 - 0.10 Rem2 Cl 0.08 Mg 0.23

0.40 max

“U”* 6.00* 4.00* 0.006 0.150 0.024 3.10 0.06 Rem2 Cl 0.11 0.40 max

1 Hydrogen shall be determined on each lot of the product shipped2 Titanium is determined by differences3 Other elements need not be analyzed nor reported unless otherwise specified* Elements added by Blended Elemental approach

Apparent Density of Titanium Powder and

Ti-6Al-4V blendsNo. Type of Titanium Powder/Ti-6Al-4V blend Gr/cm3

1 RMI Sodium Reduced Titanium Sponge Fines 1.41

2 Deeside Sodium Reduced Titanium Sponge Fines 1.20

3 Domestic Titanium Powder “A”

Domestic Titanium Powder “A” Processed by ADMA

0.18

0.65

4 Domestic Titanium Powder “D” 1.25

5 Ti-6Al-4V blend made with RMI Titanium Powder 1.53

6 Ti-6Al-4V blend made with domestic Titanium Powder “D” N/A

7 Ti-6Al-4V blend made with Titanium Powder Material “K” 1.53

BE Ti-6Al-4V Strip Produced by Direct Powder Rolling

12” wide Ti-6Al-4V strip from domestic powder “A”

Microstructure of Blended Elemental Ti-6Al-4V

(Sodium Reduced Ti powder)Direct Powder Rolling + Sintering 99+% density

Microstructure of BE Ti-6Al-4V (Sodium Reduced Ti powder)Direct Powder Rolling + Sintering

Widmanstatten (Basket Viewed type) mixed with equiaxed elements which should provide good combination of mechanical properties

Mechanical PropertiesBE Ti-6Al-4V

(Sodium Reduced Titanium Sponge)

Weld ability - No

SampleNo.

Tensile Strength

(KSI)

Yield Strength(0.2%)

Elongation%

Reduction of Area,

%

HardnessHRC

Modulus MSI

12345

151.10152.92152.28151.70151.78

128.30128.96127.53128.25129.24

7.859.207.757.256.30

14.6314.3113.0111.227.92

32.3331.8332.4732.2033.00

17.1016.8017.7016.6016.00

Microstructure of BE Ti-6Al-4V (Domestic Powder ”A”)

Direct Powder Rolling + Sintering 99+% density

Oxygen content is 0.147%;

Microstructure of BE Ti-6Al-4V (Domestic Powder ”A”)

Direct Powder Rolling + Sintering 99+% density

Microstructure of BE Ti-6Al-4V (Domestic Powder “D”)

Direct Powder Rolling + Sintering

Mechanical Propertiesof BE Ti-6Al-4V

(Domestic Powder “D”)

Alloy 1 is low Oxygen content Ti-6Al-4VAlloy 2 is high Oxygen content Ti-6Al-4V

Sample ID

Tensile,psi

Yield,0.2% offset,

psi

Elongation, %

Reduction of Area,

%

Modulus, Mpsi

1-1 132,900 116,400 10.0 14.6 16.54

1-2 133,100 117,600 10.0 16.0 16.16

1-3 134,600 117,900 10.0 13.8 15.72

2-1 138,100 123,200 9.0 11.4 16.93

2-2 138,300 121,400 10.0 10.7 16.39

2-3 137,000 121,600 8.0 9.9 16.94

Weld ability - No

New Innovative Titanium Powders

• Magnesium Reduced Titanium Sponge Powder (Innovative Kroll Process) - Powder “K”

• Cost-Effective Hydrogenated Titanium Powder From Magnesium Reduced Sponge (Powder “U” – U.S. Patent No. 6,638,336 B1 )

Chemistry of Ti Powder Produced by Innovative Kroll Process

(Powder “K”)(wt.%)

Ni Fe C Ca Mg Si N O2 Cl Ti 0.06 0.10 0.03 0.06 0.23 0.05 0.01 0.27 0.062-0.1 balance

Microstructure of Blended Elemental Ti-6Al-4V (Powder “K”)

Direct Powder Rolling + Sinter 94% density

Mechanical PropertiesBE Ti-6Al-4V (Powder “K”)Room Temperature Tensile Test ASTM E8-04

SampleNo.

Tensile Strength

(KSI)

Yield Strength(0.2%)

Elongation%

Reduction of Area,

%

Modulus MSI

1234

149.70159.70160.60161.80

147.90147.50148.30145.60

1.03.03.02.0

0.20.22.52.4

17.1016.7016.3016.30

Weld ability - No

Chemistry of Magnesium Reduced Hydrogenated Titanium Powder

Powder “U”

C H2 N O2 Cl Fe Si Ni Fe Ti

0.006 3.10 0.024 0.150 0.11 0.06 0.002 0.04 0.006 Balance

Microstructure of Blended Elemental Ti-6Al-4V (Powder “U”)

Direct Powder Rolling + Sinter 98% density

Microstructure of Blended Elemental Ti-6Al-4V (Powder “U”)

Direct Powder Rolling + Sinter 98% density

Mechanical Properties of Blended Elemental Ti-6Al-4V

Powder ”U”

Weld ability - Maybe

Compact UTS,MPa

YS,MPa

El.,%

RA,%

Oxygen,wt.%

Ti-6Al-4V 127 115 3 7 0.39Ti-6Al-4V

(Hydrogenated Ti)138 122 12.5 29 0.21-0.25

BE Ti-6Al-4V/TiAlComposite Sheet

Ti-6Al-4V

Ti-6Al-4V matrix (plate like)

Reaction zone at the interface between Ti-6Al-4V matrix and TiAl matrix

Ti-48Al-2Cr-2Nb matrix (fully lamellar);

Ti-6Al-4V

Interface

TiAl

TiAl

Conclusions

1. Ability to manufacture C.P. Ti, Ti-6Al-4V and gamma titaniumaluminides (TiAl) foils, sheets, and plates by low cost direct powder rolling/sintering process was demonstrated for all titanium powder sources used in this study.

2. Foils, sheets and plates from single layer and multiple layers produced by cost effective direct powder rolling/sintering process demonstrated near full theoretical densities (over 99% of theoretical).

3. Additional activities need to be performed for optimization of the direct powder rolling and sintering processes to produce foils, sheet, and plates and multilayered composite structures from titanium alloys and titanium aluminides and develop the properties data bases for these products.

Low Cost Titanium Components for Armor and Structural Applications

Jane W. Adams (1), Walter N. Roy (1), Vlad A. Duz (2), V.S. Moxson (2)

(1) US Army Research Laboratory, Weapons & Materials Research Directorate, Aberdeen Proving Ground, Maryland 21005, USA (2) ADMA Products, Inc, 1890 Georgetown Road, Hudson, Ohio 44236, USA. This presentation is related to the direct powder rolling process for producing titanium and titanium alloy plates and covers the activities performed against a cooperative agreement between the U.S. Army Research Lab and ADMA Products, Inc. on manufacturing low cost P/M Ti-6Al-4V alloys for armor and structural applications. Titanium alloys exhibit attractive mechanical properties, good corrosion resistance and low density, but they are expensive. The presented direct powder rolling (DRP) process has the potential to produce plate/strip/sheet/foil products from Titanium and its alloys at cost effective manner. Blended elemental (BE) powders are used in this DRP process. In the BE method, titanium powders and appropriate alloying additions (generally in the form of a cost-effective master alloy such as Al-V) are blended together and cold consolidated by directly roll-compacting to form strip, sheet or plates of near final thickness. Subsequent heat treatment produces materials which has tensile properties equivalent to those of the ingot metallurgy and meet the MIL-DTL-46077F specification requirements for armor plate. This presentation reviews the general powder rolling process, microstructures, properties, and ability to produce composite multi-layer strip. The results of this study also demonstrate that the advanced Gamma Titanium Aluminides/Titanium alloy composite plates may be also produced cost effectively by direct powder rolling process.

INTRODUCTION Titanium alloys offer the outstanding properties and expending higher volume applications of low-cost Titanium alloy plates, sheets and foils may be driven by the need for lighter weight, lower cost, environmentally friendly, and more reliable materials for industrial and military usage. Reduced weight is the goal for various systems including commercial and military aircrafts, automotive applications, ground and air vehicles, missiles, munitions, etc. Titanium is highly desirable in these applications because of its combination of high strength, low density, excellent fatigue related mechanical properties and outstanding corrosion characteristics [1-3]. However, the cost of titanium, produced by conventional technology is high, compared to steel and aluminum which is a result of high extraction and processing costs [4-7]. The powder metallurgy (P/M) is an attractive method which can eliminate the casting of ingots, forging, the multiple hot rolling of slab, and much of the hot rolling, together with annealing and other ancillary processes (Figure 1).

In the basic process for the production of strip by the direct roll compaction of powder, the fine, irregular powder is allowed to fall from a feed-hopper into the roll nip. It is drawn through the nip partially by friction between the powder and roll surface, that is by a form of pump action, and partially by gravitational force (Figure 2). Multiple composite strips, for instance Ti/Ti-6Al-4V/Ti may be produced by this direct powder rolling process [8]. Subsequent processing involves sintering, further cold reduction, an additional sintering or annealing operation and - if required - one or more temper rolling passes to produce the final finished product. Direct rolling of titanium and titanium blended elemental powders (DPR), such as Ti-6Al-4V alloy has a great potential and could be the preferred manufacturing process for producing flat products (foils, sheets, plates) for various applications. The attractiveness of direct powder rolling continues to increase as capital, equipment, labor, and energy costs escalate since it has potential for lower requirements for all these areas compared with most alternative methods of current Titanium alloy plate production. The Direct Powder Rolling (DPR) process has the following attractive features:

1. Low Capital Cost compare with melting, forging, etc.; 2. Adaptability and versatility, including ability to roll multilayer structures (for instance Ti-

6Al-4V/TiAl/Ti-6Al-4V tri-metallic composite sheets, etc.), rapid prototyping, etc.; 3. Fewer operating steps compared with melting, forging, etc.; 4. Availability of low cost raw materials;

Conventional INGOT

FINISHED STRIP

Direct Powder Rolling Elemental Ti Powder

Alloying Powders BLEND

FINISHED STRIP

POWDER ROLLING

RE-ROLL

SINTER

ANNEAL

FORGING

ANNEAL ROLL

ANNEAL RE-ROLL ANNEAL

ETC.

ETC.

Figure 1: Comparison of the Conventional Metallurgy Process with the Direct Powder Rolling Process for Ti-6Al-4V Alloy Strip Manufacturing.

5. Precision control of composition and ability to use high purity metals; 6. Applicable to composite type mixtures or immiscible components which currently cannot

be produced by the conventional methods; 7. Absence of texture and uniformity of microstructures and properties in longitudinal and

transverse directions; The powder metallurgy (P/M) approach to produce flat products (foil, sheet, plate) by low cost direct powder rolling process (DPR) was investigated by Du Pont back in 1950s and 1960s. This company could produced a titanium sponge by sodium reduction process, this sponge was reduced to powder which was ideally suited for DPR process to produce sheet and to extrude the green compacted billets to bar, tubing, and shapes [9, 10]. Commercially Pure (C.P.) Titanium sheet and Ti-6Al-4V sheet (BE powders) were produced by compacting powder continuously in the nip between two rolls. Through the development of a feed hopper and an edge control system, sheet with high green strength and green density in excess of 90 percent of theoretical was produced [11, 12]. The green sheet was coiled and sintered off line in a continuous, inert gas, sintering furnace and final rolling resulted in high-strength alloy foils with typical Ti-6Al-4V properties. Imperial Clevite had been employing DPR Titanium process since late 70s and had demonstrated capability to manufacture high strength titanium alloys (e.g. Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo) foil for honeycomb structures to obtain large, light weight, high stiffness panels by the beginning of 1980s [8]. Du Pont and Imperial Clevite never tested market in high volume application of P/M Ti-6Al-4V and other advanced Titanium alloys. The major drawback was associated with weld ability issue related to powder metallurgy Titanium alloys or unacceptable porosity of the finished Titanium alloy strip (theoretical density of the sintered strip was in the range of 95%). The presence of chlorides (up to 0.10 weight percent) trapped within the P/M microstructures volatilized rapidly during welding and caused a buildup of salt on the tungsten welding electrodes that resulted in an unstable arc. It was estimated that satisfactory weld ability would be reached at a chloride level of 0.005 present or less and achieving these chloride levels was judged at that time to be impractical from the manufacturing and cost standpoints. Other offsetting factors were: absence of domestic high volume Titanium powder producer, high cost of available Titanium powders, competition with proven and well established technologies, and lack of clear guidelines in planning and carrying out a development project. Technology has advanced significantly since Du Pont’s and Imperial Clevite’s work. A new method for production of low cost and extra low chlorine content Titanium powder, the Armstrong Process, has been recently developed by International Titanium Powder, L.L.C., a U.S.A. company [13]. The Armstrong Process reduces TiCl4 vapor in a molten stream of Na to produce high purity Ti powder. ADMA Products, Inc. obtained a patent for low cost process to manufacture Titanium powder by modified Kroll process [14]. Other processes are being developed are well outlined and described in [15] are mostly produce the Titanium powder rather than sponge or other shapes of titanium. In this article, potentially cost-effective powder metallurgy titanium production method will be evaluated and will be used to make Ti-6Al-4V plates: Direct Powder Rolling (DPR) approach to

produce continuous foils, sheets and plates (with length over 120”) and advanced Gamma Titanium Aluminides/Titanium alloy composite plates. EXPERIMENTAL PROCEDURES The immediate goal of this process development was to demonstrate the feasibility of Direct Powder Rolling (DPR) of titanium foil, sheet and plate using the Blended Elemental (BE) approach. This approach schematically is shown in Figure 2. Preliminary work carried out by ADMA Products, Inc. has demonstrated that use of blended elemental powders (Commercially Pure Sodium Reduced Titanium powder and 60%Al+40%V master alloy added to achieve the required Ti-6Al-4V composition) gives the near-full density (over 99% of theoretical), desired chemistry, microstructure, and chemical homogeneity to meet high demand for commercial applications in a cost effective manner [3, 16 - 18]. While these characteristics are not optimized for manufacturing foils, sheets and plates, and DPR processes are not well established, this study was concentrated on demonstration of feasibility to produce Ti-6Al-4V sheet/plate and composite multilayered sheet and plates by Direct Powder Rolling (DPR) approach. This approach was demonstrated on prototype scale equipment built under Cooperative Agreement between the U.S. Army and ADMA Products, Inc.

Figure 2. Schematic of the Direct Powder Rolling Process. Various titanium powder sources were used in this study: calcium reduced powder, Sodium and Magnesium reduced titanium sponge fines produced by the various suppliers, manufactures, and Armstrong powder described above. Particle size of these powders was under 150 microns. These titanium powder were blended with 10% by weight 60%Al/40%V master alloy to produce the desired Ti-6Al-4V alloy and elemental powders were used to produce the required Gamma Titanium aluminide compositions by BE approach.

The following commercially Pure (CP) Titanium powders produced by the various suppliers were evaluated as the potential candidates for low cost direct powder rolling process to produce plates, sheets and strips: 1) Sodium Reduced Titanium sponge fines; 2) Domestic Titanium powder “A”; 3) Domestic Titanium Powder “D”; 4) Ti powder produced by modified Magnesium reduction process (Material-“K”); 5) Ti powder produced by modified Kroll process (Material-“U”); The chemical compositions of different titanium powders used for direct powder rolling experiments are shown in Table 1.

Table 1. Chemical Composition of Titanium Powders Used for Direct Powder Rolling

Experiments

Powder Al C Cl Fe H2 Mg N Na O2 Ti Sodium reduced <0.05 0.122 0.21 <0.05 0.096 <0.10 0.07 0.12 0.177 Bal.

Modified Mg Reduction

“K”

- 0.03 0.08 0.10 - 0.23 0.01 - 0.27 Bal.

Modified Kroll “U”

- 0.006 0.11 0.06 3.10 0.74 0.024 - 0.15 Bal.

Domestic “A” <0.001 0.005 0.003 <0.001 0.005 0.019 0.009 0.055 0.15 Bal. Domestic “D” 0.01 0.012 0.018 0.037 0.03 - 0.023 0.12 0.188 Bal.

Various Ti-6Al-4V blends were made by Blended Elemental approach (BE) by blending 90% of the Titanium powders with 10% of Master Alloy (60% Al + 40% V) to meet the MIL-DTL-46077F chemical composition presented in Table 2.

Table 2. MIL-DTL-46077F Chemical Composition of Ti-6Al-4V

Other3 Class Al V C O N H1 Fe Ti Each Total

1 5.50-6.50

3.50-4.50

0.04 max

0.14 max

0.02 max

0.0125 max

0.25 max

Rem2 0.10 max

0.40 max

2 5.50-6.75

3.50-4.50

0.08 max

0.20 max

0.05 max

0.0150 max

0.30 max

Rem2 0.10 max

0.40 max

3 5.50-6.75

3.50-4.50

0.08 max

0.30 max

0.05 max

0.0150 max

0.30 max

Rem2 0.10 max

0.40 max

4 0.08 max

0.30 max

0.05 max

0.0150 max

Rem2

The direct powder rolled and sintered Ti-6Al-4V strips produced from the various C.P. Titanium powders were tensile tested in the as sintered conditions, i.e. no optimization of the microstructures and mechanical properties by heat treatments or thermo mechanical treatments were performed in this study.

RESULTS AND DISCUSSION

Various thicknesses (0.020”-0.100”) and densities (50-99+%) single layer C.P. Titanium, Ti-6Al-4V, TiAl and composite Ti/Ti-6Al-4V/Ti and Ti-6Al-4V/TiAl/Ti-6Al-4V strips were produced by DPR/Sintering. To produce near-full theoretical density foils, sheets and plates, the green density achieved in direct powder rolling process should be in access of 60% of theoretical. Green strip can be coiled and handled effectively, and sintered in batch or semi-continuous vacuum furnaces. The microstructures of sintered to near-full density sheet and foil for P/M Ti-6Al-4V alloy are shown in Figure 3-6 and chemistries of the sintered strips produced from the various Titanium powders are listed in Table 3.

Table 3. Chemical Composition of PM Ti-6Al-4V

Other3 Class Al V C O N H1 Fe Ti Each Total RMI 6.00* 4.00* 0.0153 0.10 0.0041 0.0110 0.003

6 Rem2 Cl 0.20

Na 0.13 0.40 max

“A” 6.00* 4.00* 0.0052 0.15 0.0086 0.005 0.001 Rem2 Cl 0.0027 Mg 0.019 Na 0.055

0.40 max

“D”** 6.00* 4.00* 0.021 0.123 0.11 0.018 0.006 Rem2 Cl 0.023 Na 0.11

0.40 max

“K”** 6.00* 4.00* 0.03 0.27 0.01 - 0.10 Rem2 Cl 0.08 Mg 0.23

0.40 max

“U”**

6.00* 4.00* 0.006 0.150 0.024 3.10 0.06 Rem2

Cl 0.11 0.40 max

1 Hydrogen shall be determined on each lot of the product shipped 2 Titanium is determined by differences 3 Other elements need not be analyzed nor reported unless otherwise specified * Elements added by Blended Elemental approach Microstructures of Gamma Titanium Aluminide (TiAl) is shown in Figure 7. Gamma titanium aluminide (TiAl) alloys with their low density (~3.9 g/cm3), good elevated temperature strength, stiffness, creep resistance and acceptable burn and oxidation resistance have excellent potential for use in high temperature aerospace applications at temperatures between 500°C to 1000°C instead of the currently used high density (~8.9 g/cm2) Ni-based superalloys. However, its poor intermediate and room temperature ductility cause conventional manufacturing operations such as rolling, forging, or drawing to be difficult for titanium aluminides, thus leading to very high cost of TiAl components (currently up to $10,000 per 30” by 12” by 0.04” sheet from an offshore source, Plansee in Austria). Direct powder rolling process for Gamma TiAl offers the substantial cost reduction of finished sheets and foils manufactured from Blended Elemental TiAl powders. This process is applicable to any TiAl composition regardless of alloying elements or addition of wiskers or other strengthening particulates. Furthermore, direct powder rolling process allows manufacturing the composite structures such as Ti-6Al-4V/Ti/Ti-6Al-4V or TiAl/Ti-6Al-4V/TiAl. Higher temperature resistance outside layers and high fracture toughness core provide the best combination of the properties for high temperature applications.

All Ti-6Al-4V blends produced with the various Titanium powders were successfully rolled to 12.5” wide x 0.020” – 0.100”thick strips to 50 – 90% green densities. All groups of strips made from the various CP Ti powder sources were successfully sintered to near full densities after preliminary optimization activities and the resulting microstructures are presented in Figures 3 – 6.

1) Sodium Reduced Titanium -100 mesh sponge fines. Ti-6Al-4V blend was used to roll the 12.5” wide strips to the various thicknesses (0.025” – 0.100” thick) and green densities (50% - 90” of theoretical densities). The strips were sintered in vacuum furnace and the resulting microstructures are shown in Figure 3.

a b

c d

Figure 3. Microstructure of Ti-6Al-4V strip after direct powder rolling (a) and sintering (99+% density). Sodium reduced Ti powder was used in blending with 60%Al/40%V master alloy. The microstructures are typically Widmanstatten (Basket Viewed type) mixed with equiaxed elements which should provide good combination of mechanical properties. Insignificant porosity observed may be a result of residual chlorine (up to 0.15%) contained in Sodium reduced Titanium sponge fines.

2) Domestic Titanium powder “A”. Two Ti-6Al-4V blends were made from two lots of Titanium powder “A” delivered by the U.S. producer as described below:

1. Lot #1 made with C.P. Titanium powder containing 0.15% Oxygen; 2. Lot #2 made with C.P. Titanium powder containing 0.20% Oxygen;

-100 mesh size Titanium powder used for both blends was blended with 60%Al + 4-% V master alloy. The blends were direct powder rolled to 12.5” wide x 0.030” thick strips and sintered to over 99% of theoretical density. The identical microstructures were obtained for both blends and microstructure of alloy produced from 0.15% Oxygen containing Ti powder is shown in Figure 4.

a b

c d

Figure 4: Microstructures of P/M Ti-6Al-4V Strips Produced from Titanium Powder “A” Containing 0.15% Oxygen (Blended with 40%Al/60%V Master Alloy) by Low-Cost Direct Powder Rolling/Sintering Process (99+ Density).

3) Domestic Titanium Powder “D” Ti-6Al-4V blend was made with 0.15% oxygen containing Domestic Titanium powder “D” and rolled to the 12.5” wide strips to the various thicknesses (0.025” – 0.100” thick) and green densities (50% - 90” of theoretical densities). The strips were sintered in vacuum furnace to 99%+ theoretical density, and the resulting microstructures are shown in Figure 5

Figure 5. Microstructures of P/M Ti-6Al-4V Strips Produced from Titanium Powder “D” (Blended with 40%Al/60%V Master Alloy) by Direct Powder Rolling/Sintering Process. As-Sintered Density is 99+% of Theoretical. 4) Titanium Powder Produced by Modified Magnesium Reduction Process, Powder “K”. Ti-6Al-4 V blend made from this powder was direct powder rolled to 12.5” wide x 0.030” thick strips and sintered to 94% of theoretical density. The resulting microstructures of the strips produced from this powder are shown in Figure 5. Further optimization of manufacturing process to produce fully dense Ti-6Al-4V strips is required.

Figure 5. Microstructures of P/M Ti-6Al-4V Strips Produced from Titanium Powder “K” (Blended with 40%Al/60%V Master Alloy) by Direct Powder Rolling/Sintering Process. As-Sintered Density is 98% of Theoretical.

5) Titanium Powder Produced by Modified Kroll Process, Material -“U”. Titanium powder produced by Modified Kroll process contains hydrogen [14] and Ti-6Al-4V blend was made from this hydrogenated titanium powder considering complete hydrogen losses during a sintering process. This blend was successfully direct powder rolled to 12.5” wide x 0.030” thick strips and sintered to 98% of theoretical density. The resulting microstructures of the strips produced from this powder are shown in Figure 5.

Figure 6: Microstructures of P/M Ti-6Al-4V Strips Produced from Titanium Powder “U” (Blended with 40%Al/60%V Master Alloy) by Direct Powder Rolling/Sintering Process. As-Sintered Density is 98% of Theoretical. The direct powder rolled and sintered Ti-6Al-4V strips produced from the various C.P. Titanium powders were tensile tested in the as sintered conditions. The objective of this testing was to determine the tensile properties of the various Ti-6Al-4V alloys produced from the various C.P, Ti powders and compare the results with the MIL-DTL-46077F Minimum Mechanical Properties requirements listed in Table 4. The results obtained on five Ti-6Al-4V alloys produced from five different C.P. titanium powders are shown in Tables 5 – 9. Tensile properties obtained on the alloys made with -100 mesh Sodium reduced Titanium powder and domestic Titanium powder “D” met MIL-DTL-46077M tensile properties specifications. Additional process optimization

activities are required for the other titanium powders which have the potentials for meeting the required tensile properties.

a b

c

Figure 7: Microstructure of Composite Blended Elemental (BE) Ti-6Al-4V/TiAl/Ti-6Al-4V Plates: a) Reaction Zone at the Interface Between the Ti-6Al-4V Matrix and the TiAl Matrix; b) Ti-6Al-4V Matrix (Plate Like); c) Ti-48Al-2Cr-2Nb Matrix (Fully Lamellar); Sodium Reduced Ti Powder Was Used in Blending with 60%Al/40%V Master Alloy.

Table 4. MIL-DTL-46077F Minimum Mechanical Properties

Class Yield Strength 0.2% Offset (psi)

Tensile Strength (psi)

Elongation, %

1 110 120 10 2 110 120 6 3 110 120 6 4 110 120 6

Ti-6Al-4V Ti-6Al-4V

TiAl

TiAl

.Table 5. Mechanical Properties of Ti-6Al-4V Alloy Produced with Sodium Reduced Titanium – 100 mesh Sponge Fines.

Table 6. Mechanical Properties of Ti-6Al-4V Alloy Produced with Domestic Titanium powder “A”. Sample

No. Tensile

strength (ksi) Yield strength

(0.2%) Elongation,

% Reduction of

Area, % Hardness

HRC Modulus,

MSI 1 2* 3 4 5

108.13 69.13 102.43 106.24 106.70

103.76 - - -

105.35

1.60 0.10 1.50 0.25 0.35

4.22 1.96 2.61 2.55 3.75

17.17 15.80 22.50 21.90 18.13

14.20 9.30 15.80 14.90 15.20

* sample 2 broke at head and before yield obtained

Table 7. Mechanical Properties of Ti-6Al-4V Alloy Produced with Domestic Titanium powder “D”.

Sample ID

Tensile, psi

Yield, 0.2% offset, psi

Elongation, %

Reduction of Area, %

Modulus, Mpsi

1-1 132,900 116,400 10.0 14.6 16.54 1-2 134,500 117,000 10.0 13.8 17.05 1-3 135,000 119,900 10.0 13.8 17.65 1-4 133,100 117,600 10.0 16.0 16.15 1-5 134,600 117,900 10.0 13.8 15.72 2-1 138,100 123,200 9.0 11.4 16.93 2-2 138,300 121,400 10.0 10.7 16.39 2-3 138,300 121,300 8.0 8.5 15.99 2-4 138,400 121,700 8.0 7.7 16.12 2-5 137,000 121,600 8.0 9.9 16.94

Alloy 1 is low Oxygen content Ti-6Al-4V Alloy 2 is high Oxygen content Ti-6Al-4V

Sample

No. Tensile

Strength (KSI)

Yield Strength

(0.2%)

Elongation %

Reduction of Area,

%

Hardness HRC

Modulus MSI

1

2

3

4

5

151.10

152.92

152.28

151.70

151.78

128.30

128.96

127.53

128.25

129.24

7.85

9.20

7.75

7.25

6.30

14.63

14.31

13.01

11.22

7.92

32.33

31.83

32.47

32.20

33.00

17.10

16.80

17.70

16.60

16.00

Table 8. Mechanical Properties of Ti-6Al-4V Alloy Produced with Titanium Powder manufactures by Modified Magnesium Reduction Process, Powder “K”.

Sample

No. Tensile

strength, (ksi)

Yield strength,

0.2% (ksi)

Elongation, %

Reduction of Area, %

Modulus, MSI

1 149.70 147.90 1.0 0.2 17.10 2 159.70 147.50 3.0 0.2 16.70 3 160.60 148.30 3.0 2.5 16.30 4 161.80 145.60 2.0 2.4 16.30

Table 9. Mechanical Properties of Ti-6Al-4V Alloy Produced with Titanium Powder manufactures by Modified Kroll Process, Powder “U”.

Sample No.

Tensile strength,

(MPa)

Yield strength,

0.2% (MPa)

Elongation, %

Reduction of Area, %

Oxygen, Wt. %

1 128 120 3.0 7 0.39 2 140 123 12.5 29 0.21-0.25 3 140 134 1.0 - 0.80

CONCLUSIONS

1. Ability to manufacture Ti-6Al-4V and gamma titanium aluminides (TiAl) foils, sheets, and plates by low cost direct powder rolling/sintering process was demonstrated for all titanium powder sources used in this study;

2. Foils, sheets and plates from single layer and multiple layers produced by cost effective direct powder rolling/sintering process demonstrated near full theoretical densities (over 99% of theoretical).

3. Additional activities need to be performed for optimization of the direct powder rolling and sintering processes to produce foils, sheet, and plates and multilayered composite structures from titanium alloys and titanium aluminides and develop the properties data bases for these products.

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