Strengthening effect of nickel and copper interlayers on hybrid laser-TIG welded joints between magnesium alloy and mild steel

AZ31B magnesium alloy and Q235 mild steel were lap joined with Ni and Cu interlayers using hybrid laser-TIG welding technique. Microstructure and mechanical properties of joints were examined. The results showed that the shear strength of Cu-added joint was a little higher than that of Ni-added joint, and the strength of both joints exceeded that of base material AZ31B Mg alloy. Microstructure in fusion zone of the both joints was in great difference and the comparison of microhardness profile in the fusion zone indicated that the morphology and distribution of intermediate phases played a vital role in strengthening the joints, and the strengthening effect of them on Cu-added joint was better than that on Ni-added joint.