Periodically layered heterostructure enhances strength-ductility trade-off in an additive manufactured dual-phase medium-entropy ferrous alloy

The quest for materials that combine defect-free composition with a balance of strength and ductility remains a perennial topic in materials science. In this paper, we achieved a heterostructure composed of periodical and dual-phase layers via laser powder bed fusion of FeCoCrNiMn-xFe mixed powders. In comparison to single-phase materials, this periodically layered microstructure enables the alloy to achieve satisfactory strength-ductility balance with yield strength, ultimate tensile strength and elongation of 581 MPa, 757 MPa and 22.8 %, respectively. Finite element simulation and experimental characterization indicated that well-architectured layered heterostructure, featuring soft and hard domains, facilitates the accumulation of large stress gradient near the interface between hard and soft layers, which not only results in the presence of multi-type deformation substructure, e.g. deformation twins, stacking faults and phase transition, but also contributes to superior heterostructure deformation induced stress, thus facilitating the additional strain hardening. This work introduces a novel approach for the composition and microstructure design of heterogeneous materials with strength and ductility synergy.