Dissimilar metal joining of magnesium alloy to zinc-coated steel by laser welding-brazing process

In automobile industry, there is a strong driving force for reducing the weight of car body by using hybrid structural body parts for improving fuel efficiency and decreasing air pollution. As one of solutions, the dissimilar combination of magnesium alloy and steel tends to be effective for the car body to save the weight while maintaining the sufficient strength for the automobiles. However, it offers great challenges and potentials to joining the dissimilar metals of magnesium alloy and steel, owing to the large differences in physical and chemical properties between them. In this work, a promising approach, laser welding-brazing process with filler wire was proposed. The weldability of dissimilar alloys of magnesium alloy and zinc-coated steel was studied. The influence of process parameters on the wetting and spreading ability of liquid filler were investigated. Furthermore, the brittle intermetallic compound phases at the interface were characterized and the mechanical properties were evaluated. From the results, failure of shear test specimen occurred at the interface from the toe of weld, which had a detrimental effect on mechanical properties of the joint.