Thermal deformation behavior and dynamic recrystallization mechanism of GH4065A alloy considering the effect of γ′ phase

In this paper, the thermal deformation behavior of GH4065A alloy at high temperature was studied by thermal simulation compression test. The effects of deformation temperature and strain rate on microstructure evolution and dynamic recrystallization mechanism were studied by electron backscattered diffraction (EBSD) technology and transmission electron microscopy (TEM). It is proved that different deformation parameters lead to significant differences in flow behavior and dynamic recrystallization behavior. The results show that dynamic recrystallization (DRX) fraction and deformation temperature have the same variation trend. In the range of high strain rate, DRX fraction increases with the increase of strain rate. During the hot deformation process, the dynamic recrystallization mechanism of the GH4065A alloy is primarily characterized by discontinuous dynamic recrystallization (DDRX) through the nucleation form of grain boundary bulging. In the γ+γ′ two-phase region, twin-induced recrystallization (TDRX) nucleation and γ′ phase-induced recrystallization (PIDRX) nucleation phenomena are present. As the deformation temperature rises above the dissolution temperature of the γ′ phase, the effects of continuous dynamic recrystallization (CDRX) and TDRX in the deformed samples are diminished. The dissolution of the γ′ phase results in the loss of its pinning effect, while the coarsened γ′ phase significantly reduces its promoting effect on the DRX nucleation process, leading to a notable increase in grain size.