Highly Alloyed Titanium Alloys Produced by Low Cost Blended Elemental Powder Metallurgy Approach

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1 Highly Alloyed Titanium Alloys Produced by Low Cost Blended Elemental Powder Metallurgy Approach M.V.Matviychuk 1, V.S.Moxson 1, V.A.Duz 1, O.M. Ivasishin 2, D.G. Savvakin 2 1 Hudson, OH, USA 2 Institute for Metal Physics, Kiev, Ukraine 1

2 Presentation overview PM BE approach for manufacturing the Ti alloys from TiH 2 powder Highly alloyed Ti compositions (beta alloys) High strength alloy Ti 1Al 8V 5Fe short overview As sintered Properties of Ti 1Al 8V 5Fe Improvement of as sintered microstructure for Ti 1Al 8V 5Fe Effect of heat treatment (HT) and thermo mechanical processing (TMP) 2

3 PM BE approach for manufacturing the Ti alloys from TiH 2 powder N Alloy Porosity, % Grain Size, mkm YS, MPA UTS, MPA El,% 1 Cp Ti Ti 6Al 4V TiH 2, Alloying Elements Powders Blending Compaction Sintering 3

4 Highly alloyed Ti compositions (beta alloys) Widely used in aerospace, automotive and other industries due to: highest strength/density ratio among all titanium alloys mechanical properties can be changed within wide range by heat treatment homogeneous microstructure and properties within large cross sections 4

5 Peculiarities of highly alloyed Ti compositions sintering - higher content of alloying elements (higher volume part of master alloys) - more complicated phase transformations (e.g. high sensitivity to cooling conditions) - complicated chemical homogenization - increased residual porosity (up to 5%) Process developed for alloys needed opt 5

6 PM BE approach for manufacturing the highly alloyed Ti alloys from TiH 2 powder Ti 10V 2Fe 3Al Porosity, % Grain Size,μm YS, MPa UTS, MPa El., % RA, % As sintered STA Porosity, % Ti 5Al 5V 5Mo 3Cr Grain Size,μm YS, MPa UTS, MPa El., % RA, % As sintered Aging TiH2, Alloying Elements Powders Blending Compaction Optimize Sintering Heat Treatment 6

7 Is it possible to produce the high strength Ti alloys with UTS>1400 MPA by Powder Metallurgy? 7

8 Highly alloyed Ti compositions Ti 1Al8V5Fe a high strength alloy developed in 1950 s Chemical compositions V Al Fe O N C Fe Guaranteed STA room temperature properties YS, MPA UTS, MPA El,% RA, % Beta Transus: 830 o C 8

9 Effect of STA on tensile properties Materials Properties Handbook Titanium Alloys edited by Gerhard Welsch 9

10 TTT diagrams Mo eq. 185 = 18 Mo eq =8.15 James D. Cotton, Proceedi ngs of 11th World Conferen ce on Materials Properties Handbook: Titanium Alloys edited by Gerhard Welsch the Mo eq = 9.5 Titanium Ti 2007 (Kyoto, Japan). pp.471 D. Eylon, 475 Beta Titan ium Alloy s in 1990 's 10

11 Effect of alloying elements on shrinkage 0,02 0,00-0,02-0,04 L/L -0,06 Ti-5553 Ti ,08-0,10 Ti-185 CpTi Temperature, C 11

12 As sintered Microstructure of Ti 185 TiH 2, Alloying Elements Powders Blending Compaction Sintering Low tensile properties High brittleness Porosity 3% 12

13 Improvement of as sintered microstructure and properties TiH 2, Alloying Elements Powders Regim e Blending Compaction Porosity, % Grain size, mkm T T T T Regular sintering Low porous sint. Porosity, % Grain Size,μm Low porous Sintering YS, MPa T1 T2 Ti 1Al 8V 5Fe T1 UTS, MPa El., % RA, % Oxygen, % T3 T4

14 Thermo Mechanical processing of Ti 1Al 8V 5Fe TiH 2, Alloying Elements Powders Ø=90mm Blending Compaction Sintering Hot rolling Post Processing Ø=16mm 14

15 Effect of thermo mechanical processing on improvement of mechanical properties of Ti 185 YS, MPa UTS, MPa El., % As-Sintered 857 ± 15 As-Rolled 1192 ± ± ± 1.5 Rolled + STA1 Rolled + STA2 Rolled + STA ± ± 4 5 ± ± ± ± ± ± 13 4 ± 1.8 Density: 97% 100% As sintered The total reduction ratio for the rod rolling process was 31:1 As rolled 15

16 RBF S N curves of Ti 185 The RBF was conducted at 10,000 RPM or Hz. 16

17 Optimized properties YS, MPa UTS, MPa El., % As-Sintered 857 ± 15 As-Rolled 1192 ± ± ± 1.5 Rolled + STA Guaranteed STA room temperature properties

18 Conclusion Highly alloyed titanium compositions with strength more then 1400 MPa (Ti 1Al 8V 5Fe) can be successfully sintered via a novel low cost powder metallurgy route using titanium hydride powder. It is especially important in case of alloys that are difficult to produce via ingot metallurgy. The microstructures of Ti 1Al 8V 5Fe were homogeneous across the entire cross section, and no segregation was observed. The controlled formation of fine grains, reduced porosity during alloy sintering, properly selected post sintering heat treatment and thermo mechanical processing parameters allow attainment of desirable properties meeting high strength requirements. 18