Evaluations of Mechanical Properties and Functionalities of the Al- and Zr-Tailored Ti-5.5Mo Shape Memory Alloys for Biomedical Applications

Due to the critical world population aging issue, biomaterials are important topics in the biomedical community. Among the biomedical materials, shape memory alloys (SMAs) are considered to be promising materials owing to their functionalities, such as shape memory effect (SME) and superelasticity (SE). Ti-Mo-Al-based alloys, which are biocompatible materials, are basic materials in the Ti-based SMAs due to the evaluation of the phase stability through the calculations of Mo and Al equivalents. This study, in addition, introduced Zr into the Ti-Mo-Al-based alloys for its highly biocompatibility and being a fine modifier to tune the phase stability. The mechanical (i.e., strength and elongation) and functional (i.e., SME and SE) properties have been investigated in this study to reveal the practicability of the biomedical applications for human usage. It was found that addition of Zr to the Ti-Mo alloy shows slight influence on the mechanical properties of the binary Ti-Mo alloy. With the addition of Al, that is, ternary Ti-Mo-Al alloys, two-stage yielding was found in the tensile examinations. Among all the alloys, the Ti-5.5Mo-4Al, the Ti-5.5Mo-4Al-6Zr, and the Ti-5.5Mo-8Al-6Zr (mol pct) alloys performed excellent shape recovery of about 100 pct in the bending and heating tests. Especially, the Ti-5.5Mo-4Al-6Zr and the Ti-5.5Mo-8Al-6Zr alloys further show high strength. Results in this study could be a guideline for the design of the fundamental Ti-Mo-Al-based SMAs.