Effect of Equiatomic Ti/Zr Substitution on the Shape Memory Effect of Biomedical Ti-Zr-Mn-Mo Alloys

In order to develop biomedical shape memory alloys with high biocompatibility, novel (Ti-xZr)-2Mn-2Mo (TZMM) alloys were designed, and their microstructure, shape memory effect and martensitic transformation behavior were investigated. In this study, Ti/Zr atomic ratio of the TZMM alloys was varied between 1, 2 and 5. The experimental results revealed that the TZMM alloys were all composed of single beta phase before plastic deformation. A certain amount of stress-induced alpha '' phase appeared after 2% strain loading. Primary beta twin-bands and secondary stress-induced martensite (SIM) alpha '' twins were activated simultaneously in the beta matrix of the TZMM alloys. (TZ)(5:1)MM alloy with a favorable {001}(beta)(beta) recrystallization texture showed relatively optimal shape memory effect within the TZMM alloys, with a recoverable strain of 2.9%. The increase of Zr content in the alloy increased the beta phase stability of metastable TZMM alloys, thereby requiring for higher stress to induce the martensitic transformation and ultimately impairing the shape memory effect of the alloys.

Automated summary

Novel (Ti-xZr)-2Mn-2Mo (TZMM) alloys were designed to develop biomedical shape memory alloys with high biocompatibility. The microstructure, shape memory effect, and martensitic transformation behavior of the TZMM alloys were investigated. The experimental results showed that the TZMM alloys were mainly composed of a single beta phase before plastic deformation, and stress-induced alpha '' phase appeared after strain loading. The (TZ)5:1MM alloy with a favorable {001}(beta)(beta) recrystallization texture exhibited the optimal shape memory effect within the TZMM alloys, while an increase in Zr content impaired the shape memory effect of the alloys by increasing the beta phase stability.