Hot deformation behavior and dynamic recrystallization kinetics of Nimonic 901 superalloy

The activation of restoration mechanisms, such as dynamic recrystallization (DRX), through hot deformation results in effective grain refinement and microstructure optimization in Ni-based superalloys. This study analyzed the appropriate hot-working parameters, DRX behavior, and microstructural evolution of a Nimonic 901 precipitation-hardened superalloy using isothermal hot-compression experiments. The mechanistic microstructural evolution of the DRX progression for the superalloy was analyzed using field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Hot compression of the Nimonic 901 superalloy was performed under a temperature range of 850 degrees C to 1150 degrees C and a strain rate of 10-4 to 1 s-1. Based on the constitutive equation established for the DRX characteristic points, an accurate kinetic model for the DRX was established to characterize the effects of plastic strain, working temperature, and strain rate on the DRX evolution. After attaining the constant parameter values in the DRX and grain size models, a grain size evolution model was derived to maintain the restored microstructure evolution as a superposition of DRX and work hardening. Finally, the established phenomenological models were used to simulate the kinetics and microstructural evolution of DRX using the finite element method (FEM). The simulation outputs agreed well with the experimental records, which indicates that FEM is an effective and accurate way to correlate macro- to microstate variables through hot deformation.