Recovery and Grain Growth Behavior of CoCrFeMnNi High Entropy Alloy

Single FCC CoCrFeMnNi with a mass of 1 kg was fabricated by vacuum levitation melting + casting. Lattice distortion caused by cold-rolling (CR) increases with thickness reduction ratio R (20%, 40%, 60% and 80%) and decreases in subsequent annealing. The recovery at 923-1023 K and grain growth at 1073-1273 K is systematically investigated. Nonlinear fitting methods are applied to study the recovery and grain growth kinetics, in which the equilibrium microhardness at a definite recovery temperature and initial grain size before the onset of grain growth are required to be fitted. The recovery activation energies of 60% and 80% CRed alloys are 148.91 kJ/mol and 155.1 kJ/mol, respectively, while the fitted equilibrium microhardness decreases with increasing T. Although satisfactory nonlinear fitted results of d(n) similar to 1/T curves, where d is grain size, can be obtained for both n = 2 and 3, the classic mechanism with n = 2 and lower activation energy (254 kJ/mol) are mainly responsible for grain growth. In all, the recovery at 923-1023 K is caused by dislocation (viscous) slide while the grain growth at 1073-1273 K can be mainly controlled by GB migration.

Automated summary

This study investigated the effects of cold-rolling and annealing on lattice distortion, recovery, and grain growth in a single crystal FCC CoCrFeMnNi. The results showed that lattice distortion increases with thickness reduction but decreases after annealing. The recovery process is dominated by dislocation slide, while grain growth is mainly controlled by grain boundary migration.