Effect of High Temperature Annealing in α + β Phase Region on Microstructure and Mechanical Properties of Ti80 Alloy Plates

The effects of the annealing temperature and the cooling mode in α + β phase region on the microstructure and mechanical properties of Ti80 alloy plates were studied. The results show that the primary α phase is sensitive to the annealing temperature and its content decreases sharply with the annealing temperature rising, but the secondary lamellar α phase increases significantly. With the increasing of the annealing temperature, the strength of Ti80 alloy decreases and the elongation changes slightly while the impact energy increases significantly. The main impact fracture mechanism of Ti80 alloy cooled by air or water after annealing is transcrystalline fracture. Compared with air cooling condition, the size of the primary α phase is smaller and the lamella being annealed at 980℃ of the secondary α phase is thinner when Ti80 alloy is cooled in the water after significant decreasing of for 60 min, which leads to the increasing of the strength, the slight declining of the elongation, and the impact energy.