Shape Memory Characteristics of Biomaterial Ti-(14-22)Zr-6Nb-2Mo-2Sn(at.%) Alloys

Since the recently reported biotoxicity of Ni, the use of Ti-Ni base shape memory alloys as biomaterial has been reduced. For this reason, Ti–Nb base superelastic alloys consisting of only non-toxic elements are being actively studied for potential use as biomaterials. In this study, the effects of Zr content and annealing temperature on the shape memory characteristics of Ti-(14-22)Zr-6Nb-2Mo-2Sn alloys were investigated using tensile tests, X-ray diffraction measurement and Electro Backscatter Diffraction (EBSD). Results showed that the maximum total recovery strain and critical stress for slip increased with increasing Zr content. This is due to the change in lattice constant with the addition of Zr. In all annealed conditions XRD analysis of the Ti-22Zr-6Nb-2Mo-2Sn(at.%) alloy revealed only β phase at room temperature, and outstanding superelasticity was observed. This means that the α/β transus temperature of this alloy is below 650oC. Maximum total recovery strain and critical stress for slip increased with decreasing annealing temperature. A maximum of 592MPa and 5.83% were obtained in the Ti-22Zr-6Nb-2Mo-2Sn(at.%) alloy annealed at 650°C for 1hr. The {001}β<110>β texture intensity increased with decreasing annealing temperature. The maximum recovery strain in the Ti-22Zr-6Nb-2Mo-2Sn(at.%) alloy annealed at 650°C for 1hr may have been caused by the well-developed {001}β<110>β type recrystallization texture.