Constitutive flow behavior and hot workability of AerMet100 at elevated temperatures

Based on the hot compression tests, the current investigation focuses on understanding, evaluating, and predicting the true stress-strain curves, the microstructural evolution of AerMet100 steel in a wide range of temperatures (1073-1473 K) and strain rates (0.01-50 s^-1). By using double-multivariate nonlinear regression, the constitutive equation was constructed at elevated temperatures, which, not only considers the influence of each independent factor on the flow stress but also the interaction among these independent factors. According to the Malas stability criterion, the processing maps were established based on the developed constitutive equation. Combined with the instability criterion m'>0 with s'>0, the optimum deformation conditions of AerMet100 were determined as temperature greater than 1330 K, and strain rate greater than 5.6 s^-1. From the observations of the microstructure after deformation, a lot of shear bands were found in the unstable domain of the processing maps, while the dynamic recovery and recrystallization can be observed in the stable domain. The formation of the adiabatic shear band from the synergy of temperature, strain rate, and deformation degree was the main reason for the deformation instability of AerMet100.