Alloy design of metastable α+β titanium alloy with high elastic admissible strain

Abstract

Owing to the high production cost of a high alloying system, the commercialization of β-Ti alloys with high elastic admissible strain (= yield strength/elastic modulus) for biomaterials is challenging. To reduce the alloying elements and maintain a high elastic admissible strain, a new alloy design of the metastable α+β-Ti alloy (Ti–4Al–2Mo–2Fe–2Cr) is proposed in this study. The microstructure of the alloy consists of an α phase with a high yield strength and a metastable β phase with a low elastic modulus. The existence of the hard α phase increases the critical stress for stress-induced martensitic transformation due to stress and strain partitioning. In addition, heat treatment in the α+β regime is an effective method for grain refinement, resulting in high strength without increasing the elastic modulus. This alloy exhibited an excellent combination of strength and ductility with a high elastic admissible strain. Moreover, electron backscattering diffraction and field-emission transmission electron microscopy were used to understand the mechanical behavior of the α+β Ti alloy.