Microstructure and mechanical properties of laminated ferrous medium-entropy alloys fabricated by direct energy deposition and post-rolling annealing treatment

•A new laminated Fe-MEA, Fe75(CoCrNi)25/Fe60(CoCrNi)40, was fabricated by DED.•After rolling and annealing, the strength and ductility show a simultaneous increase.•Grain refining, decrease of dislocation density are thought to be the reason.•The strength is higher than that predicted by ROM due to interface constraint.•The good ductility is attributed to the strain transferring between layers. Laminated ferrous medium entropy alloy (Fe-MEAs), Fe75(CoCrNi)25/Fe60(CoCrNi)40, was successfully fabricated by direct energy deposition (DED). Due to the component mixing during DED process, a transition layer with face-centered cubic (FCC) and body-centered cubic (BCC) dual-phase was obtained in the Fe60(CoCrNi)40 layer after rolling and annealing. This dual-phase exhibits higher strength compared to a single FCC phase, thereby enhancing the overall strength of the material. During the deformation process of the laminated material, interface constraint will lead to high yield strength, resulting in performance superior to that predicted by the rule of mixtures. Moreover, the transition layer plays an important role in strain transferring and shows greater strain-hardening ability than the other two layers, enhancing the overall ductility of the laminated alloy.