Preparation of pure α″-phase titanium alloys with low moduli via high pressure solution treatment

A low-modulus Ti-30Zr-5Al-3V (wt%, TZAV-30) alloy with pure α″-phase was successfully prepared by high pressure solution treatment (HPST). The X-ray diffraction (XRD) results indicate a gradual structural change from hexagonal (α′) to orthorhombic (α″) martensite in the TZAV-30 alloys treated by various pressures from 1 GPa to 5 GPa. The Young's moduli of all treated TZAV-30 alloys were derived from the tensile stress-strain curves. Among them, the alloy with pure α″ martensite phase was found to have the lowest modulus of ∼34 GPa, near the modulus of human bone. To study the origination, we summarize an approximately linear relationship between the Young's modulus and average number of valence electrons per atom (i.e. e/a value) for all α″-phase Ti alloys. The TZAV-30 alloy with pure α″ martensite phase has the low e/a value, which determines the low Young's modulus. The current study suggests that HPST is a totally new and effective route to develop the low-modulus Ti alloys as biomedical applications.