Laser welding of aluminum and 304 stainless steel with Cu and Cu/Ni/Co tri-metallic interlayers: microstructure and mechanical properties

Oscillating laser welding of 6061 aluminum alloy (Al) and 304 stainless steel (304 SS) was carried out with the introduction of Cu and Cu/Ni/Co tri-metallic interlayers. Results showed that trimetal interlayerthe highest tensile strength could reach 130 MPa and 142 MPa for joints with introduction of Cu and Cu/Ni/Co interlayers, which improved by 11.1% and 21.4% comparing to that without interlayer. This enhancement is attributed to the reduced formation of hard and brittle Fe-Al intermetallic compounds, and the newly formed interface structure consisting of Al 2 Cu, FeNi 3 , Al 13 Co 4 phases. Fracture analyses revealed that joints with Cu interlayers showed a brittle fracture, while Cu/Ni/Co interlayers exhibited a mixed ductile-brittle mode. This study offers a feasible strategy for strengthening Al/304 SS hybrid joints using multi-metallic interlayers.