Effect of Process Parameters and Tool Pin Profiles on Microstructural Evolution and Mechanical Properties of Friction Stir Welded AA5052

In this paper, friction stir welding (FSW) of AA5052 alloy has been performed using three different tool pin geometries (threaded cylindrical, hexagonal and tapered). Tool rotational speeds of 800, 1000 and 1200 rpm and welding traverse speeds of 60, 80 and 100 mm/min were used as the process parameters during experimentation. Microstructural and mechanical analyses of the welded joints were performed. The strain-hardening behaviour of the sample was also analysed. It was obtained that the tapered pin tool produced joints with the least strength of 20.5 MPa, while the threaded pin tool produced the highest joint strength of 178.4 MPa. Very high tool rotational and welding speed also resulted in poor welding efficiency. The threaded pin tool samples had a higher hardening capacity value compared to all other samples. Finer reformed grains were observed at the nugget zone of the welded sample as compared to the parent material. It was also observed that the threaded and hexagonal pin tool produced finer grains compared to the tapered tool. The ductile fracture was observed for most of the specimens. Tunnelling defects were seen for tapered tools, particularly at higher speeds.