Microstructure and properties of interlocking Cu/Al bimetallic composites by porous lattice additive combined with vacuum liquid infiltration

Inspired by biological structures observed in insects and other organisms, this study aimed to enhance the mechanical performance of copper/aluminum bimetallic composite interfaces. A biomimetic structure featuring mechanical interlocking was designed and fabricated onto the surface of a copper substrate. The filling behavior, microstructural characteristics, and shear fracture mechanisms of copper/aluminum biomimetic interlocking composites, fabricated via a combination of selective laser melting (SLM) and vacuum infiltration casting, were systematically analyzed. The aluminum melt demonstrated excellent filling quality within the biomimetic structures, forming distinct 'mortise-and-tenon' interlocking features. Intermetallic compounds diffusion exhibited regional variation at the bimetallic interface, with intermetallic compounds near the copper side being both more abundant and exhibiting higher hardness compared to other diffusion zones. Shear testing demonstrated that the biomimetic interlocking structure markedly outperformed both traditional lattice and unstructured composite interfaces. Under shear loading, the copper/aluminum composite initially exhibited robust resistance to shear deformation. However, sudden brittle fracture subsequently occurred within the aluminum regions located in the intermetallic compounds diffusion zones between structural elements, leading to a rapid decline in mechanical properties. After the mechanical properties declined to a critical threshold, the copper structure experienced predominantly ductile fracture, ultimately resulting in complete mechanical failure at the bimetallic interface.