Parameter optimization and mechanism of laser-arc hybrid welding of dissimilar Al alloy and stainless steel

Laser-cold metal transfer arc hybrid welding of 6061 Al alloy and AISI304 stainless steel (304SS) was carried out. Bead morphologies and intermetallic compound (IMC) layer characterizations of the joints were studied in detail. The optimal parameter range for accepted bead appearances (OPRBA) without surface and interface defects was obtained, and the growth mechanism of the IMC layer was summarized. The results showed that the nonuniformity in the thickness and shape along the fusion zone/304SS interface from the top surface to the bottom increases with increasing heat input and is more sensitive to laser power because the interface temperature is dominated by a high-temperature laser keyhole throughout the molten pool. As the welding parameters are within the OPRBA and the heat input is within the range of 80-110 J/mm, the joints are stronger than 130 MPa and the corresponding IMC layer thickness is at the range of 3-6.5 mu m. The kinetic analysis showed that a controlling interface temperature no more than 1,120 A degrees C may limit the growth of the IMC layer.