Optimization of the intermediate layer friction stir spot welding process

Abstract

Friction stir spot welding was performed for joining sheets of 2024 and 6061 aluminum alloys, which is otherwise difficult using conventional welding techniques. The presented approach utilizes an intermediate layer to avoid the keyhole problem. Design of experiment analysis was carried out to evaluate the influence of process parameters. The optimized set of parameters led to the fabrication of sound joints with strength properties exceeding twice the applicable standard requirements as discussed with the evidence of branched hook formations with extensive penetration. Tool rotational speed was determined to be the most significant parameter influencing the mechanical performance. The failure mode revealed itself as sheet tearing-nugget pull out in the joints produced under optimum conditions with various sized dimples apparent on the fracture surface.