Microstructure development and alloying elements diffusion during sintering of near-beta titanium alloys

Two near-beta alloys, Ti-5Al-5Mo-5V-2Cr-1Fe and Ti-10V-3Fe-3Al, were produced by the blended element powder metallurgy technique. The use of (i) elemental powders with the Al-V master alloy in the case of Ti-5Al-5Mo-5V-2Cr-1 Fe and, (ii) the complex Al-Fe-V master alloy in Ti-10V-3Fe-3Al has highlighted the influence of different alloying elements and their combination on microstructure evolution and chemical homogenisation. While Fe has the fastest diffusivity in Ti and its addition improves the density of both sintered alloys it also results in accelerated rates of grain coarsening. The combination of Al and V in the master alloy powder inhibits the diffusion of V into the Ti matrix. The unexpectedly slow diffusion of Cr at the early sintering stage in Ti-5Al-5Mo-5V-2Cr-1Fe was attributed to the formation of surface oxides on the Cr powders.