Microstructural and Mechanical Properties of Walking Friction Stir Spot Welded AA 6061-T6 Sheets

In order to increase the strength of the joint, a novel spot welding process named walking friction stir spot welding(WFSSW) has been applied for AA 6061-T6 joints using a tool movement over a distance of 15 mm. This process was carried out for four different tool rotational speeds and a better static shear strength was achieved at a tool rotational speed of 900 rpm. Macro and microstructural analysis were made in order to analyze the local material microstruture evolution. The variation of microhardness in different regions of the weld was analyzed. Fatigue tests were conducted on lap-shear specimens at a stress ratio of R=0.1. Two different fracture modes were observed under both quasi-static and cyclic loading conditions. The fracture surfaces were analyzed by using optical and scanning electron micrographs.