Dynamic recrystallization mechanism of γ and α phases during the isothermal compression of γ-TiAl alloy with duplex structure

Abstract

The dynamic recrystallization (DRX) mechanism of Ti-42.89Al-4.59Nb-2.01Cr-0.25Cu-0.1Fe-0.59Si-0.07W-0.004Se with duplex structure was investigated via electron backscatter diffraction (EBSD) when isothermal compression was conducted at the deformation temperatures of 1100–1250 °C, strain rates of 0.001–0.01 s−1 and height reductions of 20%–50%. The DRX nucleation mechanisms in the γ phase during the isothermal compression were the grain boundary bulging and progressive lattice rotation, and the latter only happened at the interior of large γ grains. The dominant growth mechanism for recrystallized γ grains changed from the strain-induced grain boundary bulging to interface immigration of γ/α phase with the increasing of deformation temperature. The DRX in the α phase was achieved through the progressive lattice rotation. Twin γ/γ interface was frequently observed during the growth of recrystallized γ grains which were nucleated through the grain boundary bulging. The formation of twin γ/γ interface was related to the low immigration rate for grain boundary to cross the interface of deformation-induced twins, and/or insufficient elements diffusion for the interface immigration of β/γ phase.