Numerical and Experimental Investigations in Laser Welding for Steel and Magnesium Alloy

The experiments of laser welding for steel and magnesium alloy in an overlap steel-on-magnesium configuration were carried out, the effect of adding Sn- foil on microstructure and mechanical properties of the weld were investigated, and numerical simulations of laser welding with/without Sn-Foil were also finished. A good agreement between the experimental results and numerical simulations for the shape and size of the molten pool can be seen. Heat transfer slows down from steel to magnesium alloy with Sn-foil, which means the thermal insulation effect, thus steel and magnesium are simultaneously melted with the larger difference in melting and boiling point. In addition, the cooling rate of steel side decreases, the diffusion time is prolonged between Fe and Sn elements, which leads to some phases, such as FeSn, Fe1.3Sn, and Fe3Sn, are formed in the transition zone of steel side, while Mg2Sn phase is found in magnesium side. Hence, adding Sn-foil is an effective way in joining steel to magnesium alloy based on the metallurgical reaction.