在环境污染日益严重的今天，汽车轻量化已成为当今社会亟待解决的问题，而钢/铝异种金属的焊接结构正是实现汽车轻量化的有效手段之一。激光焊具有焊接速度快、能量密度高、焊接变形小等特点，因此采用激光焊对钢/铝异种金属进行焊接。研究结果表明，当焊接速度为20 mm/s、焊接功率为0.82~0.83 kW时，采用“钢上铝下”的搭接形式可获得成形良好的焊接接头。未添加中间层的接头界面处存在连续分布的及岛状的金属间化合物区，其组织主要为Fe₃Al、FeAl、FeAl₂、Fe₂Al₅和FeAl₃，其中部分FeAl₃呈针状形貌。添加Fe-B-Si中间层的钢/铝界面金属间化合物区边界趋于平整，厚度减少，且岛状区和针状FeAl₃数量减少。通过拉剪试验证明，Fe-B-Si中间层的添加可提高接头的力学性能。

With increasingly serious environmental pollution,automotive lightweight has become an indispensable problem to be solved,and using welding structure of dissimilar metal for steel/aluminum is an effective means to solve the problem of lightweight. Due to rapid speed,high energy density and small deformation,laser welding is regarded as one of prospective methods to join steel to aluminum successfully. It is shown that when welding speed and laser power are 20 mm/s and 0.82-0.83 kW with steel above Al alloy,the formation quality of the lap joint between steel and aluminum joint without interlayer is well. The continuous and island Fe-Al intermetallic compounds forming at the interface of the welded joint are Fe₃Al,FeAl,FeAl₂,Fe₂Al₅,FeAl₃,and some of FeAl₃ show needle-like morphology. When Fe-B-Si is used as interlayer,the interface is more flat,the thickness of Fe-Al intermetallic compounds becomes thinner and the number of island zone and needle-like FeAl₃ decreases. The tensile-shear testing shows that the addition of Fe-B-Si can improve joints’ mechanical property.