Interface characteristics and mechanical behavior of additively manufactured multi-material of stainless steel and Inconel

Recently, direct energy deposition (DED) has been attracting considerable attention in metal additive manufacturing due to its capability of producing multi-materials and composition gradient materials with a high degree of geometrical design freedom and relatively high productivity compared to powder bed fusion processing. In this study, layered multi-materials of austenitic stainless steel (SS316L) and nickel-based superalloy (IN718) were fabricated using DED processing. The produced multi-materials showed a 500 mu m thick composition gradient material zone (CGZ) at the interface between the SS316L/IN718 because of dilution. Further, in the CGZ, closer to the SS316L side, fine cracks containing the brittle Laves and NbC phases are detected. Despite the presence of cracks, the multi-material samples showed higher yield strength and ultimate tensile strength than those calculated by rule-of-mixtures. It is attributed to hetero-deformation-induced hardening by the evolution of geometrically necessary dislocations near the CGZ during tensile deformation.