Microstructure evolution during aging heat treatment and its effects on tensile properties and dynamic Young's modulus of a biomedical β titanium alloy

Abstract

The microstructure evolution during aging heat treatment and its effects on the tensile properties and dynamic Young's modulus of a biomedical β titanium alloy Ti–10Mo–6Zr–4Sn–3Nb were investigated. The results demonstrated that a large amount of isothermal ω phase precipitated from the matrix after aging at a low temperature of 400 °C, and the formation mechanism of the ω phase was dominated by the collapse of the {222} plane collapse. With the increase of aging temperature, the ω phase was gradually replaced by α phase, and the morphology of the α phase changed from spherical to needle-like. Furthermore, the increase of the aging temperature accelerated the aging precipitation of the alloy. The results on the mechanical properties revealed that the presence of a large amount of isothermal ω phase can lead to a high dynamic Young's modulus of the alloy after aging at 400 °C, and cause the brittle fracture. The alloy composed of β+ω+α or β+α microstructures exhibited the higher strength and ductility, and lower dynamic Young's modulus than that composed of β+ω phase. The increase of the α phase content during aging at higher temperature, can lead to an significant enhancement of the dynamic Young's modulus.