Abstract
M.Tech. (Engineering Metallurgy)
The purpose of the research was to successfully weld AA6063 using Friction Stir Spot Welding (FSSW) and furthermore, to understand how the process parameters have an influence in the evolving metallurgical, mechanical and corrosion properties. Aluminium alloy (AA) 6063 sheets with a 2 mm thickness were used for this research study. FSSW was performed on the prepared aluminium sheets by varying the tool rotation rate at 600, 900 and 1200rpm and the dwell time at 10 and 15 seconds. The evolving microstructures, hardness properties, shear tensile behaviour, X-ray diffraction characteristics and the corrosion behaviour of the as-received material as well as the welds were studied. It was seen that the tool rotation rate played a crucial role in the testing of the mechanical properties. As the tool rotation rate increased at a constant dwell time, a smooth and debris free spot weld were seen, more HAZ formations became visible and more intermetallic phases of aluminium magnesium (AlMg) were formed although with very low peaks. Furthermore, the hardness properties increased as well up to a certain limit then decreased, and the corrosion properties to ASW (artificial Se Water) improved and the tensile shear strength improved. It would then be recommended to produce spot welds at 900rpm tool rotation rate at 10 and or 15 seconds for applications where the hardness is significant. Applications where corrosion is significant like in the marine industry, the ideal spot weld to produce would be at 600rpm for 10 seconds. A spot weld produced with an increasing tool rotation rate from 900rpm to 1200rpm at 15 seconds would also be an acceptable material in sea water. In applications where a higher tensile shear strength is required, the recommended spot weld to produce would be the one produced at 1200rpm tool rotation rate at 10 and/or 15 seconds.