为了在汽车制造业中实现节能环保的目的，铝合金在车身材料中的应用是实现汽车结构轻量化的重要途径。然而，钢/铝异种材料的连接问题尚未得到解决。考虑采用搅拌摩擦焊方法连接钢/铝异种材料，通过控制搅拌针的压入量，获得两种不同结合方式的接头：一种是搅拌针进入钢材中，形成机械+冶金结合的接头；另一种是搅拌针不进入钢材中，仅通过热传递的方式将摩擦热量传输到钢/铝冶金界面上形成冶金结合的接头。对形成的异种材料接头进行剪切测试和连接界面观察。研究结果表明，钢板上的镀锌层对钢/铝接头的形成具有重要影响。在机械+冶金结合的接头中，钢/铝之间的冶金界面层较厚，主要由Al、Zn元素组成；而在冶金结合接头中，界面层的厚度仅为2～3 μm，且主要由Fe、Al元素组成，并对影响接头强度的影响因素进行探讨。

In order to save the fuel consumption and reduce the pollution, aluminum alloy is one of the most acceptable materials for weight reduction in vehicle body assembly. However, how to join aluminum alloys and steels is an unsolved problem. Friction stir welding is tried to join aluminum alloy and zinc coated steel. The steel-aluminum dissimilar materials lap joints are manufactured by friction stir welding in two ways. One is that the pin is pressed into the steel material to cause a mechanical and metallurgical bonding between the dissimilar materials. Another is that only a metallurgical bonding between the dissimilar materials is formed by the heat flow from the friction of the tool and the aluminum material. The lap joints are shear tested and the interface between steel and aluminum materials are observed. It is shown that the zinc coating on the steel plate has an obvious effect on the joint forming between steel and aluminum and there is an obvious difference in shear strength and failure mode between metallurgical and mechanical-metallurgical bonding joints. In mechanical-,metallurgical bonding joint, the interface layer between steel and aluminum materials is thick and composed of aluminum, zinc phase while in metallurgical bonding joint, the thickness of interface layer is about 2-3 μm and it is mainly composed of the intermetallic compound of Fe-Al. And the factors influencing joint strength and failure mode of steel-aluminum friction stir welding joint are also investigated.