Friction stir welding of dissimilar aluminum and copper alloys: A review of strategies for enhancing joint quality

Friction stir welding (FSW) has emerged as a promising technique for joining dissimilar aluminum (Al) and copper (Cu) alloys, which are increasingly used in various industries owing to their unique properties. However, significant differences in the physical, thermal, and mechanical properties of Al and Cu pose challenges for achieving high-quality joints. This review comprehensively examines strategies for enhancing the joint quality of FSWed Al-Cu dissimilar alloys. The microstructural evolution and intermetallic compound (IMC) formation at the Al-Cu interface during FSW are discussed in detail. The effects of process parameters, such as tool rotation speed, traverse speed, and tool geometry, on the mechanical properties and fracture behavior of the joints were analyzed. Furthermore, various strategies for improving joint quality are reviewed, including process modification through optimized tool offsetting and material positioning, ultrasonic-assisted FSW, submerged FSW, stir zone modification using interlayers and reinforcement particles, external cooling and heating techniques, and joint design optimization. The effectiveness of each strategy in refining the microstructure, suppressing detrimental IMC formation, and enhancing the mechanical properties was evaluated based on the findings of previous studies. The research demonstrates that joint quality strongly depends on the precise control of process parameters and material positioning, with tool offsets of 1–2 mm toward the aluminum side consistently producing superior results. Modern assisted techniques have shown remarkable improvements in joint performance, with ultrasonic-assisted FSW and submerged FSW enhancing the tensile strength by up to 42 % through better control of the heat input and intermetallic compound formation. This review focuses on advanced strategies aimed at overcoming these challenges, including ultrasonic-assisted FSW, submerged FSW, and innovative interlayer techniques. Additionally, the review provides a comprehensive analysis of recent developments in process optimization, microstructural refinement, and mechanical property enhancement to achieve high-quality Al-Cu joints and offers guidance for selecting appropriate strategies to meet specific application requirements.