Effect of laser offsets on joint performance of laser penetration brazing for magnesium alloy and steel

The experiments of laser penetration brazing for magnesium alloy and steel were carried out, and the effect of laser offsets on mechanical properties and microstructure of the welds was investigated. In the range of 0.4-0.8 mm, with the increase of laser offset, the tensile strength of the joints increased firstly and reduced afterward. In particular, at 0.6 mm laser offset, the average tensile strength could reach a maximum of 185 MPa, which was attributed to the defect-free joining of magnesium alloy to steel. If laser offset exceeded the optimized range (0.5-0.7 mm), the defects of welding crack or incomplete fusion would occur at the interface. As it could be noticed from hardness distribution, a rapid increase in hardness was found near the interface, which had some relations with the coarse microstructure and high element concentration of the interface.