Micromechanical modeling of work hardening for coupling microstructure evolution, dynamic recovery and recrystallization: Application to high entropy alloys

A dislocation density-based multiscale constitutive model is developed to describe the hot deformation of high entropy alloys. The work hardening process of high entropy alloy is divided into several stages according to the change of hardening rate. As crystalline material, high entropy alloys are regarded as two-phase materials. In the current study, a physical-based constitutive model with three key microstructural state variables, cell mobile dislocation density, cell immobile dislocation density and wall immobile dislocation density, is proposed to simulate the phases deformations. The physical mechanisms including strain hardening, dynamic recovery, and recrystallization are considered in describing the evolution of dislocation densities. It is noted that the competition and interaction among the three mechanisms result in a typical hardening behavior of high entropy alloys. The dislocation density-based constitutive model is embedded in the modified Mori-Tanaka scheme to describe the hardening behaviors of two-phase materials with an elastic phase cell wall and an elastic-inelastic phase cell interior. The model is applied for simulating the hardening curves of CoCrFeMnNiC_0.5 high entropy alloy at different temperatures and strain rates. Compared with experimental data, it shows that the developed model can describe hot deformation of high entropy alloys with reasonable accuracy. The macroscopic inelastic strain in the Mori-Tanaka scheme is calculated by a classical plasticity method. The simulation results show that the modified method can give a more accurate prediction compared to the average inelastic strain of all phases.