Study on the Structural Characteristics and Mechanical Properties of 6061 Aluminium Alloy Friction Stir Welding Joint
The 3 mm thick 6061 aluminium alloy sheet was welded by friction stir welding.The surface morphology,microstructure and mechanical properties of the welded joint were observed and analyzed after welding.The results show that the welding quality of 3 mm thick 6061 aluminium alloy sheet is good and there are no defects on the surface and inside of the weld when the rotating speed of the stirring head is 1300 r⋅min-1 and the welding speed is 700 mm⋅min-1.The structure of the base material is slender strip,and the structure of the weld is fine equiaxed crystal.The structure near the heat engine affected zone is elongated and deformed.The micro-structure of the heat engine affected zone,heat affected zone and welding core zone on the forward side is significantly different,and the grain shape changes are more obvious and the boundary is clearer.The strength of the welded joint is abut 74%of the actual strength of the base metal,and the average tensile strength is 239.5 MPa.The fracture location is about 8.5 mm from the heat affected zone of the weld surface center,and the fracture and tensile direction are inclined about 50°.There are a large number of tear edges and dimps on the fracture surface,which shows the main characteristics of ductile fracture.The main fracture type is ductile fracture.The main form of fracture is ductile fracture.
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