Microstructure and tensile properties of hot fogred high Nb containing TiAl based alloy with initial near lamellar microstructure

High Nb containing TiAl based alloy with a nominal composition of Ti-44Al-8Nb-0.2W-0.2B-Y (in at%) exhibiting near lamellar microstructure was fabricated. Cylindrical blanks were quasi-isothermal forged at 1275 °C for 0.05 s−1, with a total reduction of 70%. The as-forged blanks were furnace-cooled (FCed) or air-cooled (ACed). The microstructure of the as-forged alloy mainly consists of remnant lamellar colonies (RL) and broken-down (BD) area caused by inhomogeneous deformation. Lamellar orientation and α2 lath thickness strongly affect the deformation of lamellar colonies. In the RL structure, the α2 phase s are remain in lath states and the γ laths recrystallized. The Blackburn relationship between the previous α2 lath and the γ lath in the RL structure is disrupted. Meanwhile, stress induced α→γ phase transformation generates the optimal perfect Blackburn relationship between the parent α2 lath and newborn γ grains. Cooling rate significantly affects the as-forged microstructure, thereby influencing the bulging rate of γ phase boundaries into α2 phases. Cooling rate also influences the tensile properties of the alloy.