Thermal deformation and dynamic recrystallization of a novel HEXed P/M nickel-based superalloy

Abstract

Hot compression tests of a novel hot-extruded (HEXed) P/M nickel-based superalloy at the temperature of 1020–1110 °C with the strain rate of 0.001–1 s−1 were carried out on a thermal simulated test machine. The microstructure evolution and nucleation mechanisms of DRX were analyzed by employing optical microscope (OM) and transmission electron microscope (TEM). The results indicate that the true stress-true strain curves of the superalloy exhibit typical features of dynamic recrystallization (DRX). The flow stress is reduced with the increasing deformation temperature or decreasing strain rate. Based on the friction-modified true stress-true strain curves, the activation energy for hot compression of the superalloy is determined to be 1175.1 kJ/mol, and the constitutive equation as well as the DRX kinetics models is established. Elevating deformation temperature or reducing strain rate can promote the proceeding of DRX. Various nucleation mechanisms of DRX are found to occur during hot deformation of the novel superalloy, which include the dominant DDRX, assisting twin-induced nucleation and CDRX, and possible γ′ stimulated nucleation.