Investigation of accelerated recrystallization behavior via electropulsing treatment in CoCrFeMnNi high-entropy alloy

Abstract

In this work, the effects of annealed temperatures (700 °C, 800 °C) and heating rates (low heating rate (LR) of 0.17 °C/s, medium heating rate (MR) of 500 °C/s and high heating rate (HR) of 4000 °C/s) on recrystallization behavior in equiatomic CoCrFeMnNi high-entropy alloy (HEA) were investigated. The mechanism of accelerated recrystallization behavior induced by electropulsing treatment (EPT) was elucidated through the evolution analysis of microstructure and geometrically necessary dislocations (GNDs). The results showed that the average GNDs density and grain size of the recrystallized region decreased with increasing annealed heating rate. At 700 °C, the average recrystallized grain size decreased from 6.1 μm to 2.2 μm with increasing annealed heating rate. At 800 °C, the HR material exhibited a higher recrystallization percentage and the corresponding decrease in average grain size from 12.5 μm for LR to 4.7 μm for HR. EPT promoted the recrystallization nucleation rate by reducing the recrystallization nucleation barrier. The better combination of grain refinement and dislocation strengthening due to heterogeneous deformation led to the yield strength (772 MPa) and fracture elongation (0.30) of the MR sample increased by ∼31% and ∼25% respectively compared with LR after annealing at 700 °C. This work provides essential insights into accelerating the recrystallization behavior and further improving the degree of grain refinement of CoCrFeMnNi HEA via EPT under the lower rolling amounts.