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A Study on Influence of Underwater Friction Stir Welding on Microstructural, Mechanical Properties and Formability in 5052-O Aluminium Alloys

Friction stir welding (FSW), a solid-state joining process is extensively using in the welding of aluminum alloy sheets. In order to save energy and reduce emission, lightweight materials like aluminum alloys were introduced into steel car body, which requires the development of effective joining processes. In the present study, welding was carried out in two different conditions, in the air (CFSW) and underwater (UWFSW) at various welding speeds to weld 5052-O aluminum alloy sheets. The effect of UWFSW on microstructural developments, mechanical properties, and formability was evaluated and compared. Grain refinement is an important opportunity to improve the mechanical properties of FS welds. Considerable grain refinement was obtained in UWFSW joints, which is smaller than that in the CFSW joints. The results indicated an increase in tensile strength, hardness, the percentage of elongation, and formability of UWFSW weld sheets. The results of the tensile test, hardness test, microstructure and fractography as in good correlation with improved properties.