Formability and mechanical property of refill friction stir spot–welded joints

The effects of rotation speed and plunge depth on macro/microstructures and mechanical properties of dissimilar 2195/2219 aluminum alloy joints produced by refill friction stir spot welding (RFSSW) were investigated. The results show that some shallow annular grooves present on the joint surfaces depending on the process parameters. Besides, hook defects are in the form of downward bending due to the higher strength of 2195 aluminum alloy. The change of rotating speed has no apparent influence on hook defect, while the increase of plunge depth makes the height of the hook defect increase significantly. The higher tensile-shear strength is associated with increased rotation speed. However, as the plunge depth increases, the tensile-shear strength rises first and then decreases. The highest tensile-shear strength measured is 6480 N, for a rotation speed of 1600 rpm, and plunge depth of 2.5 mm. Besides, there are two kinds of fracture modes present: the plug fracture and the shear-plug fracture.