The effect of precursory α and ω phase on microstructure evolution and tensile properties of metastable β titanium alloy
Ruixue Zhang, Yingjie Ma, Min Qi, Sensen Huang, Sabry S. Youssef, Guoqiang Xi, Jianke Qiu, Jiafeng Lei, Rui Yang, Ping Wang
Abstract
The microstructure evolution and tensile properties in a metastable β titanium alloy, Ti–5Al–5Mo–5V–3Cr-0.6Fe alloy with different aging conditions were investigated. The microstructure evolution of ω and α phase precipitated during low-temperature aging was characterized by the dilatometer test and transmission electron microscopy. The results show that the nanoscale ω phase formed during low-temperature aging cannot affect the tensile properties due to its small size which fails to change the deformation mechanism or strengthen the β phase. Meanwhile, the small size ω phase also fails to assist secondary α (αs) nucleation and refine αs during high-temperature aging due to ω dissolution. The α phase precipitated preferentially during low-temperature aging plays a considerable role in refining lamellar αs by occupying the space of β matrix that hinder the growth of lamellar αs. The α+β solution-treatment with two-step aging successfully refines the lamellar αs which in turn increased the tensile strength with small reduction of ductility.