Investigation of mechanical and microstructural characteristics of friction stir spot welded joints of aluminum sheets

In this work, the principle of (Friction Stir Welding ,FSW) process used to produce spot welded lap joint of aluminum sheets with (2.5 mm) thickness sheet with different welding parameters. Different welding rotational speed have been selected to show the effect of rotational speed change, the selected tool rotational speed was (710, 900, 1400 RPM) with the same welding time (15 sec.). Another experiment conducted with the same rotational speed and different welding time (30 sec) to show the effect of welding time. Mechanical and microstructural properties of welded joints have been studied also. Results of welded joints show that; there is an optimum rotational speed for maximum shear stress of welded spot when all other parameters are constant .The results show that; grain size in the stirred zone is smaller than that in the parent material which improve the weld zone properties. Based on this study and results obtained, spot welds can be produced using this welding process with good mechanical and microstructural properties for aluminum sheets.