Metallurgical joining of aluminium and copper using resistance spot welding: microstructure and mechanical properties

This paper investigates the melting phenomena, joining mechanism, microstructure evolution, and mechanical properties of the Al/Cu dissimilar joints made using resistance spot welding. A metallurgical bonding between Al and Cu is achieved via the reaction-diffusion between liquid Al and solid Cu (i.e. brazing mechanism). The reaction layer was featured by the in-situ formation of an ultra-thin Cu-rich Al-Cu intermetallic compound at the joint interface, on-cooling formation of coarse and thick theta-Al2Cu as the primary phase for hyper-eutectic solidification and formation of ultrafine lamellar alpha-Al/theta-Al2Cu eutectic structure. It is shown that the peak load and energy absorption of the Al/Cu joints are controlled by the effective length of the solid/liquid reaction zone and the thickness of the theta-Al2Cu primary solidification phase.