Hot Deformation Behavior and Dynamic Recrystallization Mechanism Transition of GH4742 Ni-Based Superalloy under Various Deformation Conditions.

In this paper, a series of hot compression tests were carried out by using a Thermecamastor-Z thermomechanical simulator in the temperature range of 1020 ~ 1140 °C and a strain rate range of 0.01 ~ 1 s⁻¹. The microstructure evolution mechanism for the GH4742 nickel-based superalloy during hot compression was studied using electron backscatter diffraction (EBSD) and scanning electron microscopy (SEM) techniques. Constitutive models for the γ + γ' double-phase and γ single-phase regions are established. The hot deformation activation energies for γ + γ' double-phase and γ single-phase microstructures are determined to be 828.996 kJ/mol and 230.707 kJ/mol, respectively. Furthermore, the internal relationship between the flow stress, hot processing map, and dynamic recrystallization (DRX) mechanism is analyzed. The results show that the high Z value is mainly located in the instability region, and the DRX mechanism is dominated by discontinuous dynamic recrystallization (DDRX), supplemented by continuous dynamic recrystallization (CDRX), particle-stimulated nucleation (PSN), and the strong pinning of γ' precipitates, which delays the development of DRX. At moderate Z values, the DRX mechanism involves the combined effect of DDRX and weak CDRX, PSN, and γ' precipitate pinning, while at low Z values, the DRX mechanism mainly involves DDRX. The transition for the DRX mechanism is extremely sensitive to the Z value. [ABSTRACT FROM AUTHOR]