Evaluation of Mechanical and Ballistic Properties of Dissimilar Aluminum Friction Stir Welded Joints

Dissimilar aluminum alloys are preferred to fabricate structural parts for naval ships, combat, and armored personnel carrier vehicles. Attaining better mechanical and ballistic behavior of dissimilar aluminum alloy joints is very difficult with conventional welding techniques. One of the most promising solid-state techniques for joining different aluminum alloys is friction stir welding (FSW). The current work aims to evaluate the mechanical and ballistic behavior of dissimilar 5083 and 6063 aluminum plates joined by the FSW process. Defect-free dissimilar FSW joint was obtained for the range of tool rotation speed (800–1200 rpm) and welding speed (30–50 mm/min). The highest tensile and impact strength of dissimilar joints was obtained for tool rotation speed (1000 rpm) and welding speed (50 mm/min). The fine crystalline size was noticed in the stir zone (SZ) region compared to the remaining regions. Microstructure and microhardness were studied in the different regions of dissimilar joints. The stirring action of the tool causes a fine layer in the SZ region and results in higher hardness compared to other regions. The heat-affected zone (HAZ) of the retreating side (RS) exhibited the lowest hardness. The ballistic behavior of base materials and dissimilar FSW joints was estimated by striking a 7.62 mm projectile. The ballistic resistance of dissimilar FSW joints was slightly lower than the AA5083 and higher than the AA6063. Fractured surfaces of tensile and impact specimens resulted in ductile failure. The ballistic fracture studies of dissimilar FSW joints confirm that shear stress completely dominated failure.