采用光纤激光器作为焊接热源的激光熔焊工艺对双相钢DP600和变形镁合金AZ31进行添加Sn箔的搭接焊研究。通过调整焊接参数获得最佳焊接成形，采用卧式金相显微镜、带有能谱仪(EDS)和电子背散射衍射(EBSD)探头的扫描电镜(SEM)和X 射线衍射仪(XRD)等观察焊接接头的微观组织、相分布、晶粒大小、元素分布和相结构组成。结果表明，添加Sn 箔激光熔焊是一种适用于Fe 和Mg 异种材料连接的有效方法，通过过渡区域形成新相可实现Mg/Fe 有效连接。实验还发现，钢上、镁下搭接激光熔焊上层双相钢的热影响区未出现明显的软化组织，焊接熔池和钢/镁接头过渡区域未见大规模氧化物和气孔缺陷，钢侧过渡区域生成FeSn、Fe1.3Sn、Fe3Sn 等Fe-Sn 相，镁侧过渡区域生成柱状枝晶的Mg2Sn相，这些新相的存在可实现钢/镁异种金属的“双向”冶金结合。

Laser welding of DP600 dual-phase steel to AZ31 deformation magnesium alloys is carried out in steelon- magnesium overlap configuration by using fiber laser as heat welding source with the addition of Sn foil. The best welding has been achieved based on the optimization of welding parameters, and microstructure, phase distribution, grain size, elements distribution and phase compositions of the welding joint are studied by using the horizontal microscope, scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) and electron backscatter diffraction (EBSD) probe and X-ray diffraction (XRD). The results show that joining iron to magnesium can be realized due to the formation of new phases in welding transition region, and it is suitable for laser welding steel to magnesium alloys with the addition of Sn foil. In addition, the experimental results suggest that there are no softening organization in heat affected zone of the upper dual-phase steel, some defects, such as oxides, pores, etc can be avoided in the transition region of steel/magnesium. Besides, FeSn, Fe1.3Sn and Fe3Sn phases are formed in the transition zone of steel side, while columnar Mg2Sn phase is seen in the transition region of magnesium side, which is befit for jointing steel/Mg dissimilar metals by the metal lurgical reaction among the iron, Sn and magnesium.