Investigation of tool offset on the microstructure and mechanical properties of AA6061-T6/PC Friction Stir Butt Welding joint

Conventional friction stir welding (FSW) is mostly applied to lap welding, which is suitable to join metal/polymer materials. In this paper, solid-state friction stir butt welding (FSBW) technology is utilized to bond the sheets with the plates of 2 mm thickness of 6061-T6 aluminum alloy (AA6061-T6) and polycarbonate (PC) in a joint design. The effects of tool offset on the temperature evolution, surface morphology, microstructural characteristics, and mechanical properties of the dissimilar joints are investigated. A sound dissimilar join with the average highest tensile strength of around 14.23 MPa is attained at the offset of 3.5 mm. Microstructural characteristics indicate an effective mechanical interlocking structure (Al anchor). The mixed fragments of polymer and metal are formed with a chaotic interface along the joint line, improving the mechanical properties of welding joints. Furthermore, a novel friction stir V shape butt welding (V-FSBW) is proposed to join dissimilar plates. The maximum tensile strength and improvement rate of the V-FSBW joint compared with conventional FSBW are 18.42 MPa and 29.4%, respectively. Results indicate that the tool offset significantly affects the welding joints, and V-FSBW can effectively increase the mechanical properties of the dissimilar AA6061-T6/PC joints.