Microstructural evolution of a Ni-Fe-Cr-base superalloy during non-isothermal two-stage hot deformation

Generally, the hot deformation behaviors and microstructural evolution of alloys are studied by isothermal hot compressive experiments. However, in the practice industrial production, the temperature in metallic parts is variant in hot forming process. In this study, the deformation mechanism and microstructural evolution of a solid-solution Ni-Fe-Cr-base superalloy during the non-isothermal two-stage hot compressive deformation are investigated. Here, the deformation temperature of the first stage is 1040 °C, while those of the second stage are 950, 980, and 1010 °C. Meanwhile, the dynamic recrystallization (DRX) behaviors and nucleation mechanisms are analyzed. It is found that the temperature of the second stage (namely the final deformation temperature) has a great impact on the microstructures. During the non-isothermal two-stage hot deformation, the DRX volume fraction increases as the deformation degree of the first stage or the final deformation temperature is increased, or the strain rate is decreased. Compared with the isothermal hot deformation, DRX behaviors are more obvious during the non-isothermal two-stage hot deformation. In addition, DRX nucleation mechanisms mainly consist of discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) during the non-isothermal two-stage hot deformation. Furthermore, DDRX plays the primary role.