Effect of Shoulder Surface Angle of Tool on Joint Properties in Friction Stir Welding of 5052 Aluminium Alloy

Friction stir lap welding of 5052 aluminum alloy was performed in the present research, and lap joints were fabricated by rotational speed of 1450 rpm and welding speed of 63 mm/min. Three tools with different shoulder surface angle (i.e. 0, 5, and 10 degrees) were designed and used. The effect of shoulder surface angle on joint properties was studied by optical microscopy and tensile-shear test. The results showed that only at angle of shoulder surface of zero-degree a continuous channel-like void was formed in the advancing side near the nugget zone and extended along the welding direction. The lap joints with the highest fracture strength has the smallest hook size, and is fractured at fraying surface rather than in the hook defect during tensile-shear test. Hook size and effective plate thickness (EPT) decreased from 4.5 to 2 and 2.25 to 1, respectively, as the angle of shoulder surface increased while the highest tensile-shear properties were obtained around 4650 N/mm at angle of shoulder surface of 10 degrees.