Lattice‐Defect‐Coordinated Microstructural Continuity and Mechanical Compatibility in LPBF‐Fabricated CoCrNi/316L Bimetallic Structures

ABSTRACT Bimetallic structures fabricated by laser powder bed fusion (LPBF) provide an effective strategy for achieving multifunctional integration, yet interfacial structural continuity and the role of lattice defects remain insufficiently understood. In this work, a crack‐free CoCrNi/316L bimetallic structure was fabricated by LPBF, and its microstructural evolution and mechanical response were systematically investigated. A continuous single‐phase face‐centered cubic structure was maintained across the entire build without the formation of brittle intermetallic compounds. A pronounced gradient microstructure was observed along the building direction, where the CoCrNi end exhibited a high density of lattice defects, whereas the 316L end showed coarser grains and fewer defects. The CoCrNi/316L interface region was characterized by grain refinement, orientation dispersion, and a high density of coordinated lattice defects, mainly originating from remelting, compositional dilution, and enhanced re‐nucleation. This defect‐mediated microstructural hierarchy resulted in a continuous hardness gradient from ∼273 HV to ∼230 HV, with a stable intermediate region at the interface. The bimetallic structure achieved a balanced strength‐ductility combination, with fracture occurring in the 316L end rather than at the interface, indicating effective load transfer and deformation compatibility. These results suggest that the coordinated distribution of lattice defects, together with grain refinement, contributes to improved interfacial microstructural continuity and mechanical compatibility in LPBF‐fabricated CoCrNi/316L bimetallic structures, providing useful guidance for the design of high‐performance multi‐material components.