Influence of process parameters on friction stir spot welded aluminum joints by various threaded tools

The flow behavior and strength of joints created using three stirring tools, with right-handed threads at different locations on their cylindrical pins, were investigated. The threading locations on the tools significantly influenced the evolution of the stir zone in the welds and caused material intermixture in various degrees at varying plunging depths. Failure joints were observed in the welds without tool rotation. Force measurements indicated that the highest torque was found in the welds at 900 rpm. Not much difference was observed in the axial force variation between the welds. The peak temperature was obtained at the measured point nearest to the tool shoulder. The maximum joint strength of over 6.5 kN was obtained in the 900 rpm weld with a 9 s dwell time.