Martensitic Transformation and Shape Memory Effect of Ti–16Nb–xZr (x = 0–8) Alloys

The influence of Zr content on the martensitic transformation behavior and shape memory effect (SME) was investigated to develop Ti–Nb–Zr high-temperature shape memory alloys. The addition of Zr decreases the peak temperature of the reverse martensitic transformation (Ap) by 19οC with 1 at % increase of Zr in the Ti–16Nb–xZr (x = 0–8) alloys, while it improves the stability of martensitic transformation by suppressing the formation of ω phase. At the same time, SME is enhanced greatly owing to the solution strengthening effect of Zr and the increase in the theoretical limit of transformation strain. The optimal Zr content for getting a high martensitic transformation temperature, an enhanced phase transformation stability and a good SME is determined to be 6 at %, where the martensitic transformation onset temperature (Ms) is 252οC and shape recovery ratio at the pre-strain of 8 is 90%.