Microstructure and mechanical properties of non-weld-thinning friction stir welded 6082-T6 aluminum alloy joints

Based on the "zero plunge depth" concept, a tapered threaded pin with triple facets and a shoulder with a circular groove were designed to solve the weld-thinning problem in the friction stir welding of 6082-T6 aluminum alloy used in the railway fields. The results indicated that the increase of the rotational speed could increase the heat input and inhibit the formation of the defects when the welding speed was constant. Compared with the parameter of 400 r/min, the process window at 600 r/min was effectively broadened, and the welding speed could reach 400 mm/min. The heat input was under the coupling effect of welding speed and rotational speed. The welding joint was prone to coarse microstructure under the high heat input, which affected the strength of the welded joint. Under the rotational speed of 600 r/min and the welding speed of 500 mm/min, the tensile strength of the joint reach 254 MPa, reaching 80% of the base material.