Titanium alloys with changeable young's modulus for preventing stress shielding and springback

While using low modulus titanium alloys, which can suppress stress shielding, several surgeons specializing in spinal diseases, such as scoliosis and spine fracture, pointed out that the amount of springback in the implant rods need to be smaller to better handle the implants during surgery; a high Young's modulus suppresses springback. Titanium alloys, which satisfy the requirements of both surgeons (a high Young's modulus, leading to suppressed springback) and patients (a low Young's modulus, leading to suppressed stress shielding) with regard to the Young's modulus of the implant rod, are currently being developed. We propose metastable Ti-12Cr as a candidate alloy for solving this problem. Ti-12Cr subjected to solution treatment (Ti-12Cr-ST) exhibits a low Young's modulus of <70 GPa. In contrast, the Young's modulus of Ti-12Cr subjected to cold rolling (Ti-12Cr-CR), is >80 GPa. This increase in the Young's modulus is due to the deformation-induced to phase. In order to develop titanium alloys with a changeable Young's modulus, we also propose the metastable Ti-30Zr-(Cr, Mo) alloy, which is developed based on the β-type titanium alloy Ti-30Zr-Mo with a low Young's modulus. Ti-30Zr-(Cr, Mo) and Ti-30Zr-3Cr-3Mo, which exhibit excellent tensile properties and changeable Young's modulus values, produce smaller springback than Ti-29Nb-13Ta-4.6Zr (TNTZ), which has a low Young's modulus. The latter is a typical β titanium alloy for biomedical applications. Thus, 3Cr3Mo is a potential candidate for biomedical implant applications.