Single crystal shear moduli of β-phase stabilized by thermomechanical treatment in TiNbSn alloys with ultralow elastic modulus

Abstract

The single crystal shear moduli is crucial to explore the origin of low Young’s modulus for β-type titanium alloys. In this study, the single crystal elastic constants of two TiNbSn alloys with Nb concentration below a critical quantity (βc) were extracted from their polycrystalline specimens using an in-situ synchrotron X-ray diffraction technique, although it was impossible to fabricate their single crystals due to the ultralow β-phase stability. The results show that the shear modulus C’ can be further reduced by decreasing the Nb concentration to below βc. Meanwhile, strong correlation between the shear modulus C44 and the Nb concentration was observed in TiNbSn alloys, although the C44 is independent on β-stabilizing elements in binary alloys. It is proposed that ultralow Young’s modulus can be realized in the alloy composition below βc by concurrently reducing C’ and C44.