MICROSTRUCTURAL ANALYSIS AND TENSILE PROPERTY STUDIES ON SPRAY COOLED FRICTION STIR WELDED ALUMINIUM ALLOY 2014

Conventional Friction Stir Welding has increased heat generation which results in improper dissolution of precipitates in Heat Affected Zone (HAZ) which develop the weakest section of the weld. In order to dissipate the heat beyond ThermoMechanical Affected Zone (TMAZ), spray nozzle with water and compressed air is used in this study. Friction Stir Welding assisted with cooling has been shown to improve the microstructure properties of the weld than normal friction stir welding process (FSW). This is because the grain structures in the nugget zone become finer when water is used as a cooling medium to dissipate the excess heat. Refined grain structure is known to improve the tensile strength and ductile properties of the weld. The welding was carried out using the spray setup at 1000 rpm and 44 mm/min. The flow rate of the nozzle setup was set to 72 ml/min. The tensile behavior of the welded specimen was then tested. The ultimate tensile strength of water cooled was obtained and compared with air cooled weld. Fracture analysis was performed using Scanning Electron Microscope (SEM) and the results are then compared. Microhardness values of various zones were then measured and compared. It was found that the weld obtained with water cooled friction stir welding possesses balanced hardness and tensile properties suitable for real life applications.