A Study on the Effect of Current Waveform on Intermetallics Formation and the Weldability of Dissimilar Materials Welded Joints (AA5052 Alloy-GI Steel) in AC Pulse GMAW

In joining aluminum alloy to galvanized (GI) steel, the huge gap of thermophysical properties, defects by zinc from the steel surface, and formation of excessive brittle Fe-Al intermetallics (IMC) are the main factors that deteriorate the joint quality. In this study, alternating current pulse gas metal arc welding (AC pulse GMAW) was suggested as a solution with a mix of electrode positive and negative modes. A 1.2 mm thick AA5052 aluminum alloy and GI steel plates were joined using 1.2 mm diameter AA4047 filler wire. A comparative study on the joint interface was conducted varying the welding current and electrode-negative (EN) ratio to investigate the effect of different welding parameters on the growth of the Fe-Al intermetallics (IMC) layer, the effect of zinc, and the mechanical characteristics of the joints. It was confirmed that the change of polarity affects the distribution of zinc element in the joints. An increase in the EN ratio suppressed the growth of the IMC layer to 3.59 mu m with decreased heat input. The maximum tensile-shear strength of the welded joints was approximately 171 MPa (78% joint efficiency) at the welding current of 50 A with 20% EN ratio.