Biocompatible low Youngʹs modulus achieved by strong crystallographic elastic anisotropy in Ti–15Mo–5Zr–3Al alloy single crystal

The elastic anisotropy of the Ti–15Mo–5Zr–3Al (mass%) β-Ti alloy, an ISO certified biomedical material, was investigated using its single crystal. It was revealed that the Youngʹs modulus exhibited pronounced anisotropy. The Youngʹs modulus was reduced to 44.4 GPa along the 〈100〉 direction in the Ti–15Mo–5Zr–3Al single crystal, that is comparable to that of human cortical bones. We determined the strategy that β-Ti alloys with extremely low moduli can be developed by reducing the electron–atom (e/a) ratio in alloys, and by suppressing the formation of the ω-phase at the same time. This new knowledge must lead to the development of “single crystalline β-Ti implant materials” as hard tissue replacements for reducing the stress shielding effect.