Overlap conduction laser welding of aluminium to steel

In the present study, a continuous wave fibre laser was used in conduction mode to join aluminium alloys to low carbon steel. Two different sets of experiments were performed: with Zn-coated steel and uncoated steel. Welding was carried out in overlap configuration with steel plate on the top aiming to conduct the heat through the steel and melt the aluminium at the interface, wetting the steel substrate. Metallurgical incompatibilities between these two participating alloys originate the formation of intermetallic phases. Therefore, restricting melting of the aluminium would limit the formation and growth of the intermetallic layer (IML). It was shown that the power density of the laser could be used such that, at the interface, aluminium only melts and the steel remains in solid state. The uncoated steel showed a regular pattern of IML formation, while the Zn-coated steel showed a different pattern of IML.