Abstract
The authors tried to butt-joint weld an aluminum alloy plate to a mild steel plate, which had thick oxide film on the faying surfaces, using friction stir welding in order to investigate the behavior of the oxide film and the process for the formation of Fe fragments scattering in Al matrix of a joint and to examine the joining process. The following results were obtained.
A rotating pin rubs the Fe faying surface and removes the oxide film from the surface, resulting in making the Fe faying surface activated. The rotating pin draws a part of Fe nearby an interface into the Al matrix by a whirling motion of the pin, and the Fe part drawn into the Al scatters in the Al matrix as fragments. At the moment that a part of Fe is drawn into the Al matrix, the oxide films on the Fe and Al are broken, and the broken oxide films remain around the Fe fragments scattered in the Al matrix. A rotating pin transfers the softened Al in a plastic flow state by frictional heat onto the activated Fe faying surface, resulting in adhering between the Fe and the Al.
