Y. Nii, H. Y. Kim, S. Miyazaki, University of Tsukuba, Tsukuba, Japan
Recently, there has been much attention paid to β-Ti alloys for biomedical applications, and many candidate alloys have been proposed. Gum Metal is one of attracting materials for biomedical applications due to its high strength and low Young’s modulus. In addition, Gum Metal exhibits unique deformation behavior such as non-linear elastic deformation behavior, high elastic deformability up to about 2.5% and very small work hardening during plastic deformation. However, the deformation mechanism of Gum Metal has not been clarified in detail. In this study, elastic deformation behavior of the Ti-23Nb-2Zr-0.7Ta-1.2O Gum Metal was investigated. The Ti-23Nb-2Zr-0.7Ta-1.2O alloy was fabricated by an Ar-arc melting method and then homogenized at 1273K for 7.2 ks in vacuum. The ingot was cold-rolled with a reduction of 98.5% in thickness and heat treated at 1173 K for 3.6 ks. In order to investigate the elastic deformation behavior of the heat treated specimens, tensile tests were carried out at various temperatures between 173K and room temperature. At the room temperature, the specimen showed non-linear elasticity with no clear yield point in the elastic region. The yield point became clear with decreasing test temperature. Obvious two-stage yielding and superelastic behavior were confirmed at 173K. It was also observed that the relationship between the apparent yield stress and test temperature satisfy the Clausius-Clapeyron equation, suggesting that the non-linear elastic behavior is related with the martensitic transformation.
Summary: Recently, there has been much attention paid to β-Ti alloys for biomedical applications. Gum Metal is one of attracting materials for biomedical applications due to its high strength and low Young's modulus. In this study, the unique elastic deformation behavior of the Ti-23Nb-2Zr-0.7Ta-1.2O Gum Metal was investigated by tensile tests at various temperatures between 173K and room temperature. Although the specimen showed non-linear elasticity with no clear yield point in the elastic region at the room temperature, the yield point became clear with decreasing test temperature. It was also observed that the relationship between the apparent yield stress and test temperature satisfy the Clausius-Clapeyron equation, suggesting that the non-linear elastic behavior is related with the martensitic transformation.
