Young's modulus change due to deformation-induced phase transformation in beta-type titanium alloys for biomedical applications

摘要

Titanium and its alloys are widely utilized for biomedical applications because of their high specific strength, corrosion resistance, and biocompatibility. In the past two decades, many researchers gave an effort to achieve a low Young's modulus for such the titanium alloys. However, Young's modulus of the metallic spinal rod that is one of the main components of spinal fixation devices should be not only low to prevent stress shielding effect for patients but also high to suppress springback for surgeons. Therefore, a novel function of biomedical titanium alloys, which is self-adjustment of Young's modulus, has been proposed recently by the authors. Deformation-induced phase transformation was introduced into P-type titanium alloys to control the Young's modulus at only deformed parts, while the Young's modulus at the non-deformed parts would remain low. In this case, the Young's modulus at the deformed parts depends on the type of deformation-induced phase. Therefore, the Young's modulus change due to deformation was investigated using several types of p-type titanium alloys. After deformation, the Young's modulus could be increased successfully by deformation-induced ω phase transformation, but was not increased by deformation-induced a' phase transformation.