Abstract：Dissimilar aluminum alloys with two types of alternate arrangement were carried out for studying material transformation and flowing during friction stir welding for material flowing. The results show that two types of rippling intervals are formed on the surface of weld with perpendicular arrangement to weld line, in which the coarse rippling intervals contributes to the cyclical gradient fluctuating material in the traverse direction. In advancing side, the intensity of material flowing and mixture is higher than that of retreating side, and the marker materials keep consecutive distribution with basal zone in the retreating side. As a result of different deformation in the weld, the boundaries are clearly formed between shoulder affected zone, probe affected zone and base metal.
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