Multi-scale microstructure strengthening strategy in CoCrFeNiNb0.1Mo0.3 high entropy alloy overcoming strength-ductility trade-off

Improving the strength of CoCrFeNi high entropy alloy with a face-centered cubic structure has been a subject of significant research in recent years. However, most strengthening mechanisms are limited by the strength-ductility trade-off. In this study, we proposed an entirely new strategy of multi-scale microstructure strengthening for high entropy alloys that significantly enhances the yield strength and ultimate tensile strength to 751 MPa and 1100 MPa, respectively, while maintaining high elongation of 15.1%. Through annealing at different temperatures, we tailored the microstructure of CoCrFeNiNb0.1Mo0.3 alloy, in which a multi-scale microstructure was achieved through inducing the micro-scale Laves phase, nano-scale precipitate and atomic-scale short-range order structure. Through Orowan bypass mechanism and shearing mechanism, the synergistic interaction effect of multi-scale reinforcements can realize a breakthrough in mechanical properties to further overcome strength-ductility trade off, and thus demonstrate a promising approach to improve engineering performance of high entropy alloys.