Abstract: In this study, a novel laminated structure featuring dual-scale heterogeneous interfaces, i.e., the micro-scale multilayer interfaces and nanoscale precipitation interfaces, was designed and fabricated by alternating stacking layers of CoCrNi medium entropy alloy (MEA) and (CoCrNi)₉₄Al₃Ti₃ MEA. The influence of layer thickness and interfacial heterogeneity magnitude on tensile behaviors was systematically investigated. Unlike conventional single-heterogeneous laminates, which exhibit only grain size gradients across interfaces, the dual-heterogeneous laminates, incorporating disparities in both grain size and precipitation, demonstrate a simultaneous enhancement in both yield strength and uniform elongation with decreasing layer thickness. This exceptional synergy of strength and ductility is attributed to multiple underlying mechanisms: first, the activation of nanoscale deformation twins, stacking faults, and Lomer-Cottrell locks during tensile deformation; second, pronounced precipitation shear hardening mediated by coherent L1₂ nanoprecipitates, which further promotes ductility; and third, the increased density of heterogeneous interfaces leading to enhanced hetero-deformation-induced hardening. These findings offer a novel and promising strategy for designing advanced laminated structures with superior tensile performance.

Key words: Laminated structures, Medium entropy alloys, Coherent interfaces, Strain gradients, Strain hardening