Superb strength and ductility balance of a Co-free medium-entropy alloy with dual heterogeneous structures

Abstract

In present work, we successfully fabricated a novel Co-free non-equiatomic Ni46Cr23Fe23Al4Ti4 medium-entropy alloy with dual heterogeneous structures, i.e. three-levels grain structures and heterogeneous L12 precipitates. Experimental results revealed the dual heterogeneous structures lead to remarkable strength-ductility synergy properties in this Co-free medium-entropy alloy, showing high yield strength and ultimate tensile strength of ~1203 MPa and ~1633 MPa, respectively, remaining an excellent ductility of ~28.7%. Further analyses about strengthening and deformation mechanisms indicated precipitation hardening and hetero-deformation induced hardening contribute the majority strength enhancement, meanwhile deformation-induced hierarchical stacking-faults networks, high density Lomer-Cottrell locks and microstructure features of heterogeneous grains and precipitates substantially facilitate the high work-hardening capacity and excellent tensile ductility. This work not only offers fundamental understanding of the strength and deformation mechanisms of the dual heterogeneous structural material, but also provides useful strength design strategy for low-price high performance high/medium-entropy alloys