Abstract: Hot compression tests are conducted by using a Gleeble–1500 thermomechanical simulator to investigate the hot deformation behavior of GH625 superalloy. Optical microscope(OM), electron backscatter diffraction(EBSD) and transmission electron microscope(TEM) techniques are employed to analyze the microstructure evolution and nucleation mechamisms of dynamic recrystallization(DRX) in hot–deformed GH625 superalloy. It is found that the dynamic recrystallization process of GH625 alloy occurs during hot deformation, and the characteristics of the true stress-true strain curve are different when the deformation temperature is different. The critical strain and stress of the onset of DRX process increase with the rising of deformation temperature. The size and fraction of dynamically recrystallized grains increase with the increasing of strain. However, there is no change in the size of the DRX grains with the continuous increasing of strain when the microstructure fully completes dynamic recrystallization. A discontinuous dynamic recrystallization(DDRX) with nucleation mechanism of bulging of the original grain boundaries is the operating nucleation mechanism of DRX of Inconel 625 superalloy. A continuous dynamic recrystallization (CDRX) with subgrain rotation and formation of twinning in the vicinity of the serrated grain boundaries, which can only be considered as an assistant nucleation mechanism of DRX, occurring simultaneously with DDRX.

Key words: GH625 superalloy, Hot deformation, Mechanism of dynamic recrystallization, Microstructure evolution