Mechanisms of Plastic Deformation in Ti-Nb-Zr-Ta Based Biomedical Alloys with Fe and Si Content

Specialized beta titanium alloys containing biocompatible elements (Nb, Zr, Ta) are increasingly considered as a material for orthopaedic implants. In this study, small additions of Fe and Si are used to increase the strength of commercial Ti-35Nb-7Zr-5Ta (TNZT) alloy. Six different advanced alloys with iron content up to 2 wt% and silicon content up to 1 wt% were manufactured by arc melting and hot forging. Flow curves were determined from tensile tests carried out at room temperature. The yield stress is increased from 450 MPa to 700 MPa due to small Fe and Si additions. Fe causes solid solution strengthening exhibited by sharp yield point and significant work hardening. (Ti,Zr)₅Si₃ intermetallic particles further increase the strength via precipitation hardening. An unusual serrated yielding behaviour of benchmark TNZT alloy is caused by twinning as shown by acoustic emission measurement and electron backscattered diffraction analysis.