Effects of Sn and Zr on the Microstructure and Mechanical Properties of Ti-Ta-Based Shape Memory Alloys

Ti-Ta binary shape memory alloys have attracted much interest due to the absence of toxic element and the low Young's modulus. However, the effects of the third element on the microstructure and mechanical property had not been well understood. In the present study, the effect of Sn and Zr additions on the microstructure and mechanical property of Ti-35Ta (at.%) alloys has been investigated. The results show that the microstructure of the solution treated Ti-Ta-based alloys compose of equiaxial grains. The alloys consist of beta-phase and alpha aEuro(3) martensite phase at room temperature, except for the Ti-30Ta-5Sn alloy which consists of only beta-phase. This is possibly due to the presence of Sn which provides a stronger beta-stabilized effect on quenching compared to Zr addition. The lattice parameter of the beta-phase increased with the increase in Sn and Zr content. The addition of Sn and Zr had caused obvious increase in the tensile strength. The corrosion resistance of Ti-Ta-based alloys was also improved by adding Sn.