Cryogenic electropulsing induced microstructure optimization of a cold-rolled CoCrFeMnNi high-entropy alloy

Microstructural evolutions of a cold-rolled CoCrFeMnNi high-entropy alloy (HEA) induced by electropulsing treatment at room temperature (RT-EPT) and liquid nitrogen temperature (LN-EPT) were investigated and compared. Finer recrystallized grains were obtained by LN-EPT compared to RT-EPT with the same discharge voltages. The recrystallization mechanisms were discussed based on the electropulsing induced athermal and thermal effects. The former mainly contributes to promoting the nucleation of grains, while the latter mainly affects the new grain growth. Meanwhile, the precipitation of the Cr-rich phase was greatly suppressed due to the electropulsing which is contrary to the annealing samples. The LN-EPT sample being treated with discharging voltage of 6 kV exhibited the highest yield strength (846 MPa) among the EPT samples due to the partially recrystallized heterogeneous microstructure. As a consequence, LN-EPT may be developed as a promising method to fabricate desired microstructure and mechanical properties.