Review of interface evolution and joint performance in ultrasonic vibration-assisted friction stir welding of aluminum with dissimilar alloys

Friction stir welding (FSW) continues to rise among the solid state joining and welding processes due to its plentiful benefits. However, it has been met with drawbacks in joining dissimilar metals/materials for application in the transportation industries, other than their initial intended application for welding aluminum alloys. The present article discusses one of the more remarkable efforts employed to control or mitigate the persistent drawbacks, i.e., ultrasonic vibration-assisted FSW, to the various dissimilar material combinations, comprising aluminum alloys with copper, steel, titanium, and magnesium alloys, as this process has a significant effect on the joint formation and strength. The broader discussions on the effects of the ultrasonic vibration presence on the surface appearance, microstructural features, materials flow, and mechanical properties of these dissimilar materials will be revealed to understand the modification caused by the assisted energy on excellent weldability and joint performance. Given the increasing interest in advanced joining techniques for lightweight and radiation-resistant structures, this review also considers the potential relevance of such dissimilar joints in nuclear applications, particularly where aluminum-based systems interface with structural or shielding components. • UVaFSW improves joint quality by reducing IMC layer thickness, refining material flow, and increasing tensile strength and elongation, leading to stronger and more durable welds. • Ultrasonic vibration raises localized temperatures, enhances heat distribution, and lowers welding load and tool torque, making the process more efficient and reducing tool wear. • It disrupts brittle IMC layers, minimizes defects like voids and cracks, and promotes better interfacial bonding, especially in challenging dissimilar joints like Al/Cu and Al/Mg. • UVaFSW shifts fracture locations away from brittle IMC zones to the weld nugget, enhancing ductility, uniform microhardness distribution, and overall joint reliability. • With proper parameter optimization, UVaFSW enables high-strength, defect-free dissimilar metal welding, making it highly suitable for aerospace, automotive, and other advanced applications.