Isothermal hot compression tests were performed on a novel as-extruded nickel-based powder metallurgy (P/M) superalloy using a Gleeble-3800 thermomechanical simulator, with deformation parameters of 1040-1100 °C and strain rates of 0.001-1 s⁻¹. The results demonstrate that the stress-strain curves exhibit three distinct types of flow behavior under different thermomechanical processing conditions: single-peak dynamic recrystallization (DRX) characteristics, discontinuous dynamic softening behavior manifested by a double-peak stress feature, and steady-state flow without significant softening at 1100 °C and 0.001 s⁻¹. The critical stress ( σ c ) and critical strain ( ε c ) for the initiation of dynamic recrystallization were determined from the work hardening rate curves, and power-law relationships between these parameters and the Zener-Hollomon parameter were established. Based on an Arrhenius-type constitutive equation, the hot deformation activation energy (Q) of the alloy during was determined to be approximately 1003.744 kJ/mol through linear regression analysis. By combining processing maps with post-deformation microstructural analysis, the optimal processing window for this alloy was identified as 1060-1080 °C with strain rates of 0.001-0.01 s⁻¹. Deformation mechanisms analysis demonstrated that continuous dynamic recrystallization (CDRX) predominated under low-temperature/high-strain-rate conditions. In contrast, discontinuous dynamic recrystallization (DDRX) progressively became the primary softening mechanism as temperature increased and strain rate decreased.
Zhao et al. (Sun,) studied this question.