Microstructure and mechanical properties of Ti/W and Ti-6Al-4V/W composites fabricated by powder-metallurgy

Tungsten-reinforced Ti and Ti-6Al-4V composites were fabricated by powder metallurgical techniques from Ti, W and Al-V powders. The microstructure of the composites consists of partially dissolved tungsten particles within an alpha/beta titanium matrix containing tungsten in solid-solution. Yield and ultimate tensile strengths increase linearly with tungsten content in the range 0-15 wt.% W and decrease near-linearly with temperature in the range 25-540 degreesC. Ductility follows the opposite trend and is within technologically acceptable values, except for Ti/15W at 315 and 425 degreesC and Ti/10W at 540 degreesC which fractured near the ultimate stress value. The Ti-6Al-4V/10W composite shows the best combination of high strength and ductility at all temperatures. At ambient temperatures, Ti/10W exhibits a stress-strain curve very similar to Ti-6Al-4V (with a slight decrease in stiffness), while eliminating aluminum and vanadium alloy elements. Further improvements in mechanical properties of these non-equilibrium composites are likely to be achieved through optimized heat-treatments, which affect the matrix microstructure and the degree of dissolution of tungsten and thus the relative importance of matrix solid-solution strengthening and composite strengthening. (C) 2002 Published by Elsevier Science B.V.