Hot deformation and dynamic recrystallization behavior of TiAl-based alloy

Abstract Hot compression and dynamic recrystallization (DRX) behavior of TiAl alloy (Ti-44Al-4Nb-1.0Mo-0.1B-0.01Y) were investigated by hot compression tests. The tests were conducted at temperature range of 1120–1240 °C with strain rate of 10 −3 ∼1 s −1 . Results show that the flow stress during hot compression is affected by deformation temperature and strain rate. The stress exponent n and activation energy Q are measured to be 2.711 and 524.67 kJ/mol, respectively. Critical strain for DRX initiation is measured, and the relationship between critical strain e c and peak strain e p can be expressed as: e c = (0.7–0.9) e p . It is found that crack in β phase as well as the decomposition of β phase result from inhomogeneous deformation between γ phase and β phase. With the decreasing of ln Z , volume fraction (referred to V f ) of lamellar colony decreases and α phase gradually “invade” from the periphery to the center part of lamellar colony. Two DRX models during the hot deformation of TiAl alloy are developed. Type I relies on the nucleation within lamellae. Type II is the DRX of α phase. If ln Z >39.6, only type I can be found in the microstructure. If 36.1