Effects of Thermomechanical Treatments on Pseudoelastic Strain Characteristics of Ti-29Nb-13Ta-4.6Zr for Biomedical Applications

Abstract

There is a possibility for β-type Ti-29Nb-13Ta-4.6Zr (TNTZ) to exhibit super-elastic characteristics, which is advantageous for biomedical applications such as orthodontic wires. Thermomechanical treatments are expected to induce super-elastic characteristics in β-type titanium alloys. Therefore, TNTZ specimens were subjected to various thermomechanical treatments, including solution treatments and severe cold rolling, wherein the second solution treatment temperature, second solution treatment time, and reduction ratio of cold rolling were varied in order to investigate the elastic deformation characteristics. One of the thermomechanical treatments induces super-elastic characteristics in a TNTZ specimen. In particular, a highest total pseudoelastic strain of 2.8% is measured in the TNTZ specimen subjected to the thermomechanical treatment at a cold rolling reduction ratio of 95%, second solution treatment temperature of 1073 K, and second solution treatment time of 0.3 ks. Tensile loading and unloading stress-strain curves of the TNTZ specimens subjected to various thermomechanical treatments indicate a high total pseudoelastic strain and exhibit three step deformation process. An α martensite phase is formed in the TNTZ specimen subjected to the thermomechanical treatment carried out under the above mentioned conditions.