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

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.