Effect of Al-foil addition on microstructure and temperature field of laser fusion welded joints of DP590 dual-phase steel and AZ31B magnesium alloy

Abstract The experiments of laser fusion welding with Al-foil addition was carried out for DP590 dual-phase steel and AZ31B magnesium alloy in an overlap steel-on-magnesium configuration. Temperature field was simulated by COMSOL finite element software for steel/magnesium laser fusion welding. The results show that when Al-foil is added, some defects, such as pores, cracks and softening in heat affected zone (HAZ), can be avoided in welding joint, the bonding strength of steel/magnesium joints is increased, heat transfer between steel and magnesium is regulated. In the case of adding Al-foil, welding pool is divided into two parts, the upper and lower pools contact each other but do not mix, the transition layer at the interface between the upper and lower molten pools mainly contains Al–Fe phases, such as AlFe, Al2Fe and AlFe3, and these new phases are helpful for promoting the metallurgical connection between the upper and lower molten pools. Hence, adding Al-foil laser fusion welding is an effective way in joining steel to magnesium alloy.