Microstructure and properties of Ti-17 powder compact prepared through powder sintering and isothermal forging

Abstract

Powder sintering and dual isothermal forging were utilised to prepare titanium alloy. Owing to the disturbance effect of residual pores during sintering, the microstructures of two sintered Ti-17 powder compacts prepared with about 80–150 and −150 mesh powders were composed of large residual pores and low aspect ratio of α platelets and small residual pores and high aspect ratio of α platelets respectively. Residual pores can be closed during the first isothermal forging above the β transus due to the excellent plastic deformation capability of the β phase. The microstructure can be effectively broken during the second isothermal forging below the β transus. Isothermal forging with 10−2 and 10−4 s−1 strain rates can obtain uniform microstructure, whereas isothermal forging with 1 s−1 strain rate just refined the microstructure non-uniformly. Closure of the residual pore and change of the microstructure’s morphology during dual isothermal forging effectively improved the ductility of the compact even though the oxygen and nitrogen contents exceeded the standard requirements.