Microstructures and mechanical properties of 7050-T7451 aluminum alloy joint welded by stationary shoulder friction stir welding

7050-T7451 aluminum alloy joint was successfully obtained by stationary shoulder friction stir welding（ SSFSW）. Weld appearance,microstructures,hardness profiles and tensile properties of the joint were measured and studied. The results show that the joint by SSFSW process has good and smooth appearance,and there is little reduction in the weld thickness. Compared with the conventional FSW,the microstructures of SSFSW joint was also significantly different. The thermomechanically affected zone is quite narrow,whose width on the advancing side is only 60 μm. The hardness profiles of joint presents"W"shape,the lowest hardness occurs in the heat affected zone near the weld nugget,the microhardness is 128 HV. The tensile strength of the joint is 486.8 MPa,which reaches up to 92% of the base metal. The fracture occurs in the heat affected zone,which is a typical ductile fracture.