Effects of phase stability and processing on the mechanical properties of Ti-Nb based β Ti alloys.

The influence of β phase stability on mechanical properties, deformation behaviours and phase composition were investigated for a series of Ti-24Nb-3Zr-2Sn-xMo alloys in response to hot and cold rolling. For the hot rolled alloys, the phase composition and deformation behaviours were largely consistent with those predicted on the basis of a Bo-Md plot and the Ms estimates. The deformation mechanisms involve growth and/or reorientation of plate-like martensite and/or twins. However, these are largely restricted in the cold rolled alloys due to the effects of grain refinement and residual stress. The cold rolled alloys exhibit the highest strengthening in combination with more limited ductility, which increased with increasing β phase stability. The moderately stable alloy, B, with e/a around 4.18 and Moeq∼10wt% gave the greatest strengthening in response to cold rolling, which was related to intense localised grain refinement.