Process and mechanical properties of cold metal transition welding of Al/Mg alloy based on adding intermediate layer Zn

Objective In the industrial production process, connection of aluminum alloy and magnesium alloy was inevitable. Due to significant difference in the thermophysical properties between aluminum alloy and magnesium alloy, brittle intermetallic compounds were prone to form during welding process, resulting in a reduction in strength of welded joints. Methods To enhance strength of welded joints, cold metal transfer welding method was employed to conduct a lap welding test on 1 mm thick 6061 aluminum alloy and AZ31B magnesium alloy plates by adding an intermediate layer of Zn foil in this paper. Welding speed was 4 mm/s, wire feed speed was 2.7 mm/s, arc voltage was 15 V, and welding current was selected as 37 A, 42 A, and 47 A respectively. Macroscopic morphology, microstructure and interface chemical composition of welded joints without intermediate layer and with intermediate layer were investigated by scanning electron microscope and optical microscope. Mechanical properties of welded joints were characterized by universal tensile testing machine. Results The results showed that addition of intermediate layer Zn improved forming quality of Al/Mg alloy cold metal transfer welded joints, changed bonding state and microstructure at the interface of dissimilar metals, and significantly inhibited generation of brittle Al-Mg compounds, thereby improving mechanical properties of welded joints. Conclusion The results of this study not only enriched thin plate welding of Al/Mg dissimilar alloys but also provided certain theoretical guidance for actual industrial production.