A comparison of Ti–Ni and Ti-Sn binary alloys processed using powder metallurgy

The simple press-and-sinter powder metallurgical technique has provided an economical route for the manufacture of components from lightweight alloys, including titanium. However, the issue of residual porosity is limiting Ti alloy use in demanding applications. The presence of a liquid phase during sintering can potentially facilitate diffusion, leading to improved densification. In the present work a comparison of liquid phase sintering mechanisms is undertaken, with either persistent or transient liquid formation, for Ti–Ni and Ti–Sn alloys, respectively. Samples are produced using blended elemental powders, with up to 10 wt% alloying addition. Compacts were uniaxially pressed, and sintered at 1200–1400 °C. The benefit of Ni addition is significant in terms of sintering, with close to full density (~99.5% of theoretical) achieved for optimised conditions. Sn additions also exhibit a beneficial sintering response, particularly at lower temperatures (<1250 °C) and for lower concentrations (i.e. 2.5 wt%), with densities exceeding 98.5% of theoretical achieved under optimal conditions. The hardening effect is clear for both alloy groups compared to commercially pure-Ti, whereas there was generally an adverse effect on the tensile properties.