Research on hot deformation behavior and constitutive model to predict flow stress of an annealed FeCrCuNi2Mn2 high-entropy alloy

Abstract

In the present study, the hot deformation and dynamic recrystallization behaviors of an annealed FeCrCuNi2Mn2 high-entropy alloy were investigated through the hot compression tests. Flow curves were evaluated within a certain temperature range (700–1000 °C) and initial strain rate range (0.001–0.1 s−1), and the corresponding microstructures were assessed. Constitutive equations with strain-dependent material constants were established for the calculation of material constants and for modeling of flow stress behavior through the analysis of true stress-strain curves. The critical and peak stress and strain (dynamic recrystallization parameters) were extracted from the work hardening rate against stress curves. These parameters were then used to determine the recrystallized volume fraction under different conditions. The results indicated that with the increase in deformation temperature and decrease in strain rate, dynamic recrystallization parameters decreased. This trend was followed by an increase in recrystallized volume fraction and grain growth, resulting in a decrease in the hardness value of the alloy. Findings further revealed that the flow stress in the annealed alloy was higher compared with that in the as-cast alloy under the same deformation conditions. Microstructural observations and the evaluation of work hardening rate against stress curves showed the typical dynamic recrystallization characteristics as the dominant softening mechanism under different deformation conditions. The activation energy of hot deformation was determined to be 437 kJ/mol. In the present study, a power equation was established between critical stress and strain and the Zener–Hollomon parameter with the exponents of 0.089 and 0.086, respectively. Moreover, the dynamic recrystallization grain size was found to be proportionate to Z−0.11.