Evolution of flow stress and microstructure during isothermal compression of Waspaloy

The evolution of the flow stress and microstructure for Waspaloy was studied in the 950–1140 °C temperature range under constant true strain rate conditions of 0.001–1 s−1 up to a true strain of 0.83 using isothermal hot compression testing. The impact of friction at the sample/anvil interface and adiabatic heating during deformation on the flow stress evolution was also examined. Mathematical models relating the flow stress to the deformation temperature and strain rate were derived using a power–law relationship. The strain rate sensitivity and the activation energy for hot deformation of Waspaloy were found to be considerably different for deformation in the subsolvus and supersolvus temperature ranges. According to the microstructural investigations, at 950 °C dynamic recovery (DRV) was the main softening mechanism. By contrast, dynamic recrystallization (DRX), partial or complete, occurred at temperatures above 950 °C and resulted in flow softening.