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
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
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 1 120 495 605 21 2 Ti 6Al 4V 1.5 150 885 975 12 TiH 2, Alloying Elements Powders Blending Compaction Sintering 3
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
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
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 2 82 1005 1100 10.6 17.9 STA 2 82 1115 1250 5.2 11.0 Porosity, % Ti 5Al 5V 5Mo 3Cr Grain Size,μm YS, MPa UTS, MPa El., % RA, % As sintered 1.5 100 1140 1244 4.87 9.21 Aging 1.5 100 1200 1304 6.8 10.3 TiH2, Alloying Elements Powders Blending Compaction Optimize Sintering Heat Treatment 6
Is it possible to produce the high strength Ti alloys with UTS>1400 MPA by Powder Metallurgy? 7
Highly alloyed Ti compositions Ti 1Al8V5Fe a high strength alloy developed in 1950 s Chemical compositions V Al Fe O N C Fe 7.5 8.5 0.8 1.3 4.0 6.0 0.25 0.5 Guaranteed STA room temperature properties YS, MPA UTS, MPA El,% RA, % 1380 1448 6.0 12.0 0.07 0.05 4.0 6.0 Beta Transus: 830 o C 8
Effect of STA on tensile properties Materials Properties Handbook Titanium Alloys edited by Gerhard Welsch 9
TTT diagrams Mo eq. 185 = 18 Mo eq. 5553 =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. 1023 = 9.5 Titanium Ti 2007 (Kyoto, Japan). pp.471 D. Eylon, 475 Beta Titan ium Alloy s in 1990 's 10
Effect of alloying elements on shrinkage 0,02 0,00-0,02-0,04 L/L -0,06 Ti-5553 Ti-1023-0,08-0,10 Ti-185 CpTi 0 200 400 600 800 1000 1200 1400 Temperature, C 11
As sintered Microstructure of Ti 185 TiH 2, Alloying Elements Powders Blending Compaction Sintering Low tensile properties High brittleness Porosity 3% 12
Improvement of as sintered microstructure and properties TiH 2, Alloying Elements Powders Regim e Blending Compaction Porosity, % Grain size, mkm T1 2.5 110-137 T2 1.9 136-204 T3 2.7 126-166 T4 2.55 156-217 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, % 3 50 875 0.4 1.9 160 862 925 0.33 13 T3 T4
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
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 ± 13 1283 ± 12 18 ± 1.5 Rolled + STA1 Rolled + STA2 Rolled + STA3 1489 ± 6 1535 ± 4 5 ± 1.0 1620 ± 16 1654 ± 10 1668 ± 15 4.7 ± 0.8 1689 ± 13 4 ± 1.8 Density: 97% 100% As sintered The total reduction ratio for the rod rolling process was 31:1 As rolled 15
RBF S N curves of Ti 185 The RBF was conducted at 10,000 RPM or 166.6 Hz. 16
Optimized properties YS, MPa UTS, MPa El., % As-Sintered 857 ± 15 As-Rolled 1192 ± 13 1283 ± 12 18 ± 1.5 Rolled + STA4 1585 1654 8 Guaranteed STA room temperature properties 1380 1448 6 17
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