Hot Deformation Characteristics and Dynamic Recrystallization Mechanisms of a Novel Nickel-Based Superalloy

The hot deformation characteristics of a novel nickel-based superalloy is investigated via the isothermal compression test in temperature range of 1000-1150 degrees C and strain rate of 0.001-10 s(-1)under the true strain of 0.8. The hot deformation characteristics of GH4065 alloy are studied here for the first time. Based on the flow stress data, it is observed the typical features of flow curves exhibit the occurrence of dynamic recrystallization (DRX) during the hot deformation process. The constitutive equation in the Arrhenius-type model is established, and activation energy (Q) is determined as 844.787 kJ mol(-1). The microstructure evolution and DRX mechanism are investigated by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) technique. The results reveal that the fraction of low angle grain boundaries (LAGBs) decrease gradually with the increase in deformation temperature, whereas the fraction of sigma 3 boundaries increase first and then decrease. For gamma + gamma ' dual-phase region, the particle-induced DRX (PIDRX), characterized by the generation of sub-grains accelerated by gamma ' precipitates pinning dislocations, and discontinuous dynamic recrystallization (DDRX) are the dominant nucleation mechanism of DRX. For gamma quasi-phase region and gamma single-phase region, the occurrence of bulged grain boundaries with twins further illustrates that DDRX plays a more significant role.