Influence of Nb Addition on Phase Constitution and Mechanical Properties of Biomedical Ti-Zr Based Alloys

The influence of Nb addition on phase constitution, microstructure and mechanical properties of biomedical equi-atomic Ti-Zr based alloys was investigated. Phase constitution of Ti-Zr based alloys containing Nb rapidly cooled from beta single phase changed with Nb addition as follows: alpha' -> alpha '' + alpha' + beta -> beta + alpha '' -> beta. Young's moduli of Ti-Zr based alloys subjected to water quenching initially decreased with increasing Nb content. The minimal value was obtained in the Ti-48Zr-4Nb (mol%) composition alloy. The Young's moduli increased in relation to the phase constitution change. In the alloys containing over 4% Nb, their principal phase was changed by subsequent cold rolling, this is mainly because beta -> alpha' and beta -> alpha '' stress-induced martensitic transformation occurred. This phase transformation resulted in a decrease of Young's modulus. Furthermore, cold rolling impartd anisotropy to the Young's modulus which caused the value to drop. The Ti-47Zr-6Nb alloy had the lowest value of Young's modulus after cold rolling in this study, 59.5 GPa.