Effect of Forging Temperature on Microstructure and Fracture Toughness of TC4 Titanium Alloy

TC4 alloys with different microstructure morphologies are obtained through forging experiments at different forging temperatures of 900 °C, 920 °C and 940 °C respectively, and the effects of forging temperature on microstructure and fracture toughness of TC4 alloys are systematically studied. The results show that as the forging temperature increases, the content of primary α phase in the microstructure decreases, while the content of secondary α phase increases. The morphology of secondary α phase transforms from fine fragmented state to flat state, and the lamellar thickness and aspect ratio gradually increase. The fracture toughness of TC4 alloy shows an upward trend, and the surface undulation degree and the shear lip zone area of the fracture surface gradually increase. When the forging temperature of TC4 titanium alloy is 940 ℃, the fracture toughness of the TC4 alloy bar is the best. That’s because larger content, thickness and length and width ratio of the secondary α phase make the crack propagation path more tortuous, which will consume more energy, contributing to better fracture toughness of the alloy.