The work aims to study the structure and mechanical properties of aluminum alloy friction stir welding (FSW). The butt welding experiment of aluminum plate was carried out through FSW in the specific form of single-sided welding double-sided forming. The tensile machine and micro Vickers hardness tester were used to test the mechanical properties of the samples. The micro-structures of base metal and welded joint were studied with Zeiss metallography and scanning electron microscope. The results showed that microstructure of the nugget zone are more uniform and finer with the increase of the rotation speed. In the heat-mechanics affected zone, there are large plate-like structures and a fine equiaxial crystal, the grain size is gradually decreasing. The average grain size of the heat affected zone showed an increasing trend. The hardness of heat affected zone is the lowest, followed by nugget zone. The tensile fracture position of the samples under different welding processes is all at the welded joint of the aluminum alloy, the fracture of the welded joint shows obvious ductile fracture characteristics. The elongation of FSW joints under 1000r·min-1 and 100mm/min is 17.1％, the tensile strength is 410MPa, the mechanical properties of the welded joint under 1000r·min-1 and 100mm/min are the best.
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