Secondary a phase evolution in the isothermal compression and heat treatment of TC8 titanium alloy

The TC8 titanium alloy was isothermally compressed in the two-phase region and followed by air cooling. The heat treatment was also carried out, in which the TC8 titanium alloy were heated to the temperatures of 900°C, 940°C, and 980°C respectively and held for 40 mm, then followed by furnace cooling (FC), air cooling (AC) and AC+550°C/180 min (AC1). The microstructure evolution was examined by optical microscope (OM) and scanning electron microscope (SEM). The morphology of secondary α phase transforms from equiaxed to lamellar morphology with the increasing of deformation temperature. However, the secondary α phase is only precipitated in AC and AC1 procedures at a temperature of 980°C, and the lamellar α phase in AC1 procedure is thicker than that in AC procedure. Combining the experimental results and the present analysis, it indicates that the hot deformation promotes the precipitation of secondary α phase.