Effect of Process Parameters in Friction Stir Welding of Dissimilar Aluminium Alloys

Abstract

Friction stir welding was invented at Welding institute, United Kingdom in the year 1991 and has ever since been proved to be one of the best solid state joining methods for materials such as aluminium and magnesium. Some of the aluminium alloys which are not able to weld (Al-Cu, Al-Zn-Mg alloy) by fusion welding techniques, which produce defects and reduce the mechanical properties on the weld nugget could be welded using friction stir welding (FSW) successfully with excellent joint efficiencies. However effect of the process parameters on the properties of weldment have not been investigated fully. In this study, 5mm thick plates of aluminium alloys AA2024 (4.4%Cu, 0.6%Mn, 1.6%Mg) and AA7075 (2.5%Mg, 1.4%Cu, 0.2%Cr, 5.6%Zn) is selected for investigation. The FSW welding process was conducted on varying the welding process parameters such as tool rotation speed (RPM), welding speed (mm/min) and tool pin profile by keeping downward force (kN) constant. The properties such as defects, macro and microstructure, micro hardness, tensile and bend behavior on welded plates were studied. Sixteen sets of butt welds were produced using straight and tapered cylindrical with left hand threaded FSW tool pins. It has been found out that defect free weld could be produced with the help of tapered cylindrical with left hand threaded tool pin with tool rotation speed of 600 RPM, welding speed of 30 mm/min and downward force of 2.5 kN