Mechanical and electrochemical analysis of AA5083-AA7075 dissimilar alloy joints fabricated by friction stir welding

Abstract This study aims to enhance high strength (AA7075), high-corrosion resistant (AA5083) dissimilar joints of Aluminum (Al) alloys employing friction stir welding (FSW) technique for marine applications. The dissimilar weld of Al alloys was fabricated with standardized FSW process parameters (i.e., 1100 rpm of tool rotational speed, 2° tilt angle, and 50 mm/min of welding speed). Detailed analysis of weld characteristics, mechanical properties, and corrosion behaviour are carried out to establish the effectiveness of the FSW technique for dissimilar welding. The hardness profiles across the weld regions revealed a notable increase in hardness within the stir zone when compared to the base metals, which is attributed to the fine-grained microstructure produced during the FSW process. The optimized FSW joint's ultimate tensile strength (UTS) is 80% of the AA7075 base metal, indicating good joint efficiency. Microstructural analysis through optical microscopy and SEM provides insights into the grain structure and phase distribution within the weld zone. The stirred zone exhibits a refined equiaxed grain structure due to the effect of dynamic recrystallization during FSW. Corrosion behavior was assessed using Tafel plots and Electrochemical impedance spectroscopy (EIS). The Tafel plots illustrated that the welded joint exhibited a corrosion potential and current density comparable to that of the base metals, suggesting that the FSW process did not lower the corrosion resistance of the materials. EIS results provided further evidence of the weld's stability in corrosive environments, with impedance spectra indicating better corrosion resistance.