Microstructures and tensile properties of a high strength β titanium alloy Ti5Al4Zr8Mo7V by near β forging and β-transus forging

State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an, Shaanxi, 710049, P. R. China

qysun@xjtu.edu.cn

Abstract

A novel high-strength metastable β-Ti alloy Ti-5Al-4Zr-8Mo-7V has been successfully developed by improved Bo-Md map combined with critical Mo equivalent criteria. Near β forging combined with different heat treatments was introduced to tailor the Bi-modal structure. The alloy exhibits good strength-ductility combination with UTS~1390 MPa and El~10% after solution treated (ST) at 800°C followed by 570°C aging. After β-transus forging combined with subsequent heat treatment, an excellent combination of strength UTS~1460MPa and El~10% is achieved which is attributed to the Tri-modal structure consisting of primary α (α_p), sub-micro α rods (α_r) and nano-scale α platelets (α_s). Plastic strain is effectively partitioned in both α_p, α_r and β matrix during deformation, which results in a more homogeneously strain distribution and improved ductility. Nano-scale distribution of α_s effectively block the dislocation motion in β matrix and strengthen the alloy.