Recovery stress and strain behavior of Cr20Mn20Fe20Co35Ni5 high entropy alloy deformed via severe plastic deformation

Abstract

The shape memory properties of the Cr20Mn20Fe20Co35Ni5 high-entropy alloy (HEA) prepared by using severe plastic deformation (via differential speed rolling) were evaluated after annealing at different temperatures by tensile testing and the effect of grain size on its recovery stress and strain behavior were examined. The obtained grain size after annealing ranged from 3.0 to 82.2 μm. As the grain size (annealing temperature) was increased, the recovery strain was increased because the amount of deformation-induced martensite formed during rolling, and the density of grain boundaries and annealing twin boundaries decreased. A maximum recovery strain of 1.2% was obtained from a sample with a large grain size of 82.2 μm, while a maximum recovery stress of 302 MPa was obtained from a sample with a small grain size of 7.1 μm. This result indicates that grain refinement can lead to enhanced recovery stress but reduces recovery strain. The optimum amount of prestrain for recovery stress and strain was 6%. Training effect due to repeated cycling was observed. The shape memory characteristics and behaviors of the present HEA are found to be similar to those of Fe-Mn-Si-based shape memory alloys. © 2023 Elsevier Inc.