Effect of Pin Shapes on Joint Characteristics of Friction Stir Spot Welded AA5J32 Sheet

The joint strength of friction stir spot welded 5J32 Al alloy was investigated according to the tool shape (threaded pin tool: TPT; cylindrical tool: CT; cylindrical tool with projection: CTP) and tool penetration depth. With increasing tool penetration depth, the vertical joint deformation increased in TPT and CT, whereas the joint diameter increased in TPT. The tensile shear load of the joint using TPT and CT did not vary with tool penetration depth, because the decreased upper plate thickness impeded the increase of the tensile shear load. That of CTP, however, rapidly increased with increasing tool penetration depth to produce a maximum tensile shear load of 4.6 kN. CTP, with its shoulder comprising a slight, broad projection, retarded the vertical joint deformation and produced good mechanical properties.