Achieving high strength and ductility in a CoCrFeNiMn0.75Cu0.25 high entropy alloy via heterogeneous structure design

Heterostructuring is an effectively strategy for overcoming strength-ductility trade-off of high entropy alloys (HEAs). In this study, a non-equiatomic CrFeCoNiMn_0.75Cu_0.25 HEA, consisting of bimodal grain structures, nano-sized precipitates/ twins, and sub-grains, was fabricated by a combination of severe plastic deformation (rolling and laser shock peening) followed by annealing. It was demonstrated that the HG structured HEAs exhibits an excellent combination of high yield strength (∼1.03 GPa) and high plasticity (∼15 %) compared to homogeneous structured alloys. Here, the enhanced twining, bimodal grains and precipitation activity contribute to significant mechanical incompatibility, which in turn promotes the hetero-deformation-induced strengthening. As a result, the heterogeneous HEA exhibited excellent mechanical properties. This approach is both straightforward and effective for enhancing the mechanical properties of HEAs, presenting a new avenue for the design of heterostructured alloys with superior strength and ductility.