Investigation of Corrosion Behavior of the AA5754 Aluminum Alloy Joined Using Friction Stir Welding Method

Abstract

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Friction stir welding (FSW) between 2 mm thickness AA 5754 aluminum alloy sheet was researched in the current research. The welded joints were qualified by its aspects, microstructural ,mechanical features and corrosion behavior at cell temperature. The effect of the conical tool geometry on the FSW AA5754 are investigated over potentiodynamic polarization, open circuit potential (OCP) monitoring, test of the susceptibility to corrosion, micro-hardness and tension tests. The thermomechanically affected zones adjacent to weld nugget are most susceptible to corrosion in the weld joints. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analyses on the stir zone suggested that, intermetallic phases of the base material were mechanically fractured, smeared and mixed to different geometries due to tool stirring. The increase in anodic reactivity in the weld zone was due to the sensitisation of the grain boundaries leading to intergranular attack. Enhancement of cathodic reactivity was also found in the nugget as a result of the precipitation of Mgrich phases.