High-quality welding of copper and aluminum by angled laser irradiation and insert metals

Copper is an important material in order to use electricity effectively, and aluminum is also an attractive material to perform lightweight construction. Laser welding of copper and aluminum is required, and there are some reports to weld copper and aluminum firmly by laser irradiation from the aluminum side. On the other hand, laser irradiation from the copper side requires high power density to generate a keyhole, which causes the strong convection of molten aluminum into copper. Thus, brittle intermetallic compounds with rich aluminum result in the deterioration of joining strength. Angled laser irradiation enables mild heat input to the aluminum side, and the combination of angled and superposed irradiation of blue and near-infrared (NIR) lasers achieved a remarkable increase of breaking strength. However, the breaking strength is still lower than the base materials. Therefore, insert materials between copper and aluminum plates were investigated by the angled irradiation of blue and NIR lasers from the copper side. The breaking strength with insert materials showed higher values in the order of titanium mesh, nickel foil, and nickel mesh, and its value with the nickel mesh was close to the tensile strength of aluminum in a cross tensile test. Further improvement of breaking strength is possible by inserting the nickel mesh between copper and aluminum plates in the case of angled irradiation of blue and NIR lasers even from the copper side.