Large spot laser assisted GMA brazing-fusion welding of aluminum alloy to galvanized steel

Through positioning the leading laser as an auxiliary role, and the trailing arc as the main heat source, aluminum alloy (Al) was joined to galvanized steel plate with lap joint. The brazed seam width w increased with the increasing of heat input. The appropriate laser-wire distance Dlw and defocusing distance df to obtain the good fusion weld appearance were 5 mm and +20 mm, respectively. The fracture position of tensile test sample was divided into brazed interface fracture (P < 0.6 kW) and HAZAl fracture (P > 0.6 kW). The maximum tensile strength of dissimilar joint reached 75% of that of Al. The shear strength was mainly decided by heat input, and the brazed seam had the highest microhardness. Joining mechanism of this process was summarized into two factors: the effective function of laser and the metallurgical function of zinc. Compared to gas metal arc welding (GMAW), large spot laser assisted GMA process improved weld appearance and enhanced the process stability and its time-efficiency.