The influence of rotational speed in the Friction Stir Welding of 6082-T6 aluminium alloy joints

Abstract

Friction Stir Welding is regarded as a great welding technique compared to other welding processes. As a welding technique, it has good advantages as well as lesser disadvantages. It is categorised as a solid-joining technique with the aid of applied force and friction. A non-deteriorating rotating tool is plunged between two materials (similar or dissimilar) to be joined at a specific rotational and welding speed. The tool is moved through the material rubbing against them, causing them to soften and fuse before they solidify. This technique is mostly used in the welding of aluminium alloys especially in the automotive, aerospace and marine industries; as it produces high-quality welds with very low porosity, lesser change in material, low distortion and low shrinkage. This research reports on the influence of rotational speeds on friction stir welded 6082-T6 Aluminium Alloy plates of 6 mm thickness. The different rotational speeds tested were, 600, 700, 800, 900, 1000 and 1200 rotation per minute (rpm). The microstructure and macrostructure were also evaluated under optical microscopes and compared. The 6082 aluminium alloy specimens were tensile tested, using the Hounsfield machine. The fractured tensile specimens underwent fracture analysis taking fractographs using the Scanning Electron Microscope (SEM). The material's hardness was tested using the Rockwell B hardness (HRB). Results show that high rotational speeds with a welding speed of 80 mm/min have a negative effect on the welds at the start and middle of weld but positive effect at the end for tensile properties and grain sizes. Rotational speed of 600 rpm was found to produce welds with higher tensile properties with smaller grain sizes. While 1000 rpm was found to be suitable to get high hardness values.