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 degrees 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 alpha(2) lath thickness strongly affect the deformation of lamellar colonies. In the RL structure, the alpha(2) phase s are remain in lath states and the gamma laths recrystallized. The Blackburn relationship between the previous alpha(2) lath and the gamma lath in the RL structure is disrupted. Meanwhile, stress induced alpha -> gamma phase transformation generates the optimal perfect Blackburn relationship between the parent alpha(2) lath and newborn gamma grains. Cooling rate significantly affects the as-forged microstructure, thereby influencing the bulging rate of gamma phase boundaries into alpha(2) phases. Cooling rate also influences the tensile properties of the alloy. (C) 2015 Elsevier B.V. All rights reserved.