On the Heterogeneity of Deformation and Fracture in Bimetallic Specimens of the C11000-Inconel 625 System

In this work, bimetallic specimens of the copper C11000-Inconel 625 system were fabricated using multi-wire electron beam additive technology. Three different sequences of component deposition were employed to produce the bimetallic specimens for investigation: Type A-nickel and pure copper were deposited side by side in parallel; Type B-layers of nickel-based superalloy were printed first, followed by the deposition of copper on top; Type C-copper layers were printed first, with nickel-based superalloy subsequently deposited on top. The influence of additive manufacturing conditions and sequence on the microstructure, static and fatigue strength, and impact toughness of the test pieces was studied. The results indicate the formation of a complex anisotropic structure in bimetals of various types during printing, driven by directional heat dissipation toward the substrate. The microstructure comprising large primary grains or dendrites elongated along the heat flow direction leads to significant differences in material properties along the printing (scanning) direction, the build (growth) direction, and at intermediate angles. Studies of the copper C11000-Inconel 625 bimetallic samples have shown that the interface between components does not exhibit inherent weakness compared to the base materials: pure copper or nickel superalloy. Tensile testing consistently reveals that fracture occurs by the adhesive mechanism in the weaker constituent, rather than at the interface.