EFFECT OF WELDING SETTINGS ON MECHANICAL CHARACTERISTICS, MICROSTRUCTURAL FEATURES, AND CORROSION PERFORMANCE IN FRICTION STIR WELDING OF DISSIMILAR AA6082-T6/7075-T6 JOINTS

This research explores the influence of welding settings (tool rotational speed, travel speed) on mechanical characteristics (tensile, micro-hardness), microstructure, and corrosion performance of dissimilar butt joints between aluminum alloys AA7075-T6 and AA6082-T6, which were fabricated by friction stir welding (FSW). The study considers three varied tool rotational speeds (1600, 2000, and 2300 rpm) in conjunction with three varied tool travel speeds (30, 40, and 50 mm/min). The butt joints were created by welding plates that were 6 mm thick. The welded specimens underwent characterization through optical microscopy, SEM, tensile testing, micro-hardness testing, and corrosion testing. Macroscopic observations of the samples revealed a range of stir zone shapes and defects that resulted from both inadequate and excessive heat input during the welding process. Analysis of the microstructure and results from the tensile testing indicated that the specimens produced using FSW settings of 2000 rpm and 40 mm/min achieved a peak ultimate tensile strength, demonstrating a value of 150 MPa. The micro-hardness values exhibited variations corresponding to changes in rotational speed, attaining a peak value of 240 HV at a rotational speed of 2300 rpm and a travel speed of 40 mm/min. The best mixing of the joined materials was achieved at a maximum welding rotational speed (2300 rpm) and medium travel speed (40 mm/min). A corrosion analysis of welded joints was conducted using a potentiodynamic polarization test in a solution containing 3.5% sodium chloride (NaCl). The welded zone (WZ) exhibits a reduced corrosion current density (I_corr), attributed to the occurrence of galvanic corrosion. The performance of corrosion within the WZ is impacted by the rotational speed and tool travel speed. Lowering the speed of the rotation tool leads to a decrease in the corrosion rate. Optimal corrosion resistance is achieved in the joint created at 2300 rpm and 30 mm/min, attributable to the suitable density and size of precipitates