Friction Stir Spot Vibration Welding: Improving the Microstructure and Mechanical Properties of Al5083 Joint

In this study, a modified version of friction stir spot welding (FSSW) is applied to join Al5083 specimens. In respect to conventional FSSW, this new method leads to better characteristics, finer grain sizes in the stir zone and higher mechanical properties. In this method, the workpiece is vibrated normal to tool axis direction during FSSW. This process is entitled friction stir spot vibration welding (FSSVW). The finite element method (FEM) was used to validate the experimental results. The FEM and experimental results had a good agreement. The microstructure of the welded zone was analyzed by scanning electron microscopy and optical microscopy. The results showed that the presence of vibration during FSSW led to more grain refinement. This was related to more straining of material in the welded zone which enhanced the dynamic recovery and recrystallization and increased the grain refinement. The results showed that grain size of welded region for friction stir spot-welded specimen was about 35% lower than that for friction stir spot-welded specimen. Mechanical properties such as tensile shear load and hardness increased as the vibration was applied. Also, mechanical properties increased as vibration frequency increased from 28 to 38 Hz during FSSVW.