Joining of AZ31 magnesium alloy and steel sheet under four different coating conditions based on gas metal arc weld-brazing

Abstract

Dissimilar joining of AZ31 Mg alloy to various steel sheets with different coatings (galvanized (GI), galva-annealed (GA), cold rolled bare (CR), and aluminized (Aluminized) steel sheets) was performed by gas metal arc brazing. An excellent weld bead appearance was obtained in all cases and the wettability of the AZ31-GI steel joint was better than that of the other brazed joints. Moreover, the AZ31-CR steel brazed joint exhibited the highest tensile-shear strength. The fracture behaviors of the four brazed joints were different and depended mainly on the chemical composition (especially the Zn content) of the coating layer. Owing to the weak bonding between the Mg-Zn eutectic phase and the Fe-Al intermetallic compound, which formed at the interface of the joint, the strength of the Zn-coated steel (GI and GA steel sheet) joints was lower than that of their non-Zn-coated counterparts.