Comparison and analysis on dissimilar metals welding of aluminum alloy to galvanized steel by different welding-brazing methods

The welding-brazing lap joints of aluminum/galvanized steel were obtained by using the pulse bypass coupling arc MIG welding (Pulsed DE-GMAW),cold metal transfer (CMT) and laser welding,respectively. The analysis on the microstructure, shape and elements of welding joint shows that these three welding methods are feasible for welding aluminum to steel,due to the low welding heat input of these methods,good weld formation can be also obtained. In addition,the mechanical properties of weld bead are measured. The results show that the tensile-shear strength of lap joint can reached 80% of the tensile strength of aluminum alloy; the sample fracture in the heat affected zone of aluminum alloy. When the heat-input and welding parameters were appropriated,it can generate a thin layer of Al-Fe intermetallic compounds on the lap joint interface under these three methods,and the average thickness of the compound layer is about 8 μm,it is confirmed that the intermetallic compounds is composed of Fe₂Al₅ and FeAl₃. The key of welding aluminum to steel is control the formation of intermetallic compound in the interface by reducing the heat input.