Effects of Sn-foil addition on the microstructure and mechanical properties of laser welding joint for dual phase steel and magnesium alloy

The aim of present research was investigating the effects of Sn-foil addition on the microstructure and mechanical properties of laser welding joint for DP600 dual phase steel and AZ31 magnesium alloy in an overlap steel-on-magnesium configuration. Results showed that when Sn-foil was added as interlayer, some defects, such as surface pit, spatter and softening in heat affected zone, can be avoided,oxide and porosity are also no obvious in the weld. A good weld surface with continuous and uniform fish scale welding line is obtained. Fe–Sn phases, such as FeSn, Fe1.3Sn, and Fe3Sn, are formed in steel side, while Mg2Sn is found in magnesium side. These new phases are favorable for realizing the steel/magnesium metallurgical connection, and adding Sn-foil laser welding is an effective way in joining steel to magnesium alloy. However, mechanical property for steel/magnesium joint is closely connected with the brittleness of Mg2Sn phase, how to regulate its brittleness is the key in order to improve the joint properties.