Achieving Superior Mechanical Properties in CoCrNiCuFe High-Entropy Alloys via Synergistic Design of Composition and...

This paper employs molecular dynamics (MD) methods to investigate the strength-plasticity design and microscopic mechanisms of CoCrNiCuFe high-entropy alloys. First, through compositional screening, it is found that the CoCrNiCu_0.5Fe_1.5 composition exhibits a favorable combination of high flow stress and moderate plastic stability among the examined candidates. Its moderate stacking fault energy effectively promotes the formation of nanotwins and martensitic phase transformation during deformation, achieving a synergistic improvement in strength and plasticity. Second, the strength of this alloy exhibits a nonmonotonic dependence on grain size, peaking at approximately 13 nm within the range investigated in this study. This critical size corresponds to the transition from the Hall-Petch effect to the inverse Hall-Petch effect. For smaller grain sizes (<13 nm), deformation is dominated by grain boundary sliding and intensive phase transformation, while for larger grain sizes, it is governed by dislocation slip and storage. Finally, introducing a grain size gradient structure within the inverse Hall-Petch region can effectively coordinate the deformation mechanisms across different zones. Even with a relatively small gradient rate (0.13), the strength significantly surpasses that of uniform nanocrystalline materials with the same average grain size (5 nm), and the strengthening effect intensifies with increasing gradient rate. This research provides theoretical foundations and specific strategies for the microstructural design of high-performance high-entropy alloys from the perspectives of compositional design and microstructural regulation.