Frustrating dislocation resistance inhomogeneity at multiscale levels to enable strength-ductility synergy in multi-principal element alloys

Designing metallic alloys of high strength-ductility synergy has remained an unremitting pursuit for many engineers and scientists. Recent advance in designing multi-principal element alloys (MPEAs) offers an ample and unprecedented space for advanced microstructure design to address this need. In this work, we investigated a strategy to push the strength-ductility trade-off envelop by utilizing multiscale local chemical inhomogeneity created on the principle of negative mixing enthalpy alloying. This is achieved in an FCC CoCrNi MPEA added with Al, Ti and V as negative mixing enthalpy elements to the host elements. This promoted the alloy to form complex structural variations at multiple scales, including short-, medium- and long-range chemical orders; at the nanoscale, L1₂ nanodomains with varying morphologies and planar fault energies within the FCC matrix; and at the microscale, a bimodal grain size distribution. Such microstructure frustrates and disunifies dislocation resistance, promoting cascading activation of various lattice deformation and hardening mechanisms, such as stacking faults, deformation twins, and L1₂ nanodomain shearing, during the deformation process. This design yields an exceptional combination of mechanical properties, with a yield strength of ∼1.3 GPa, an ultimate tensile strength of ∼1.92 GPa, and a uniform elongation of ∼28% at ambient temperature. Our findings may provide potential reference for designing various degrees of local chemical ordering in alloys to manipulate the movement of dislocations for achieving high strength and ductility synergy. © 2026 Acta Materialia Inc.