The role of pressure in improving the properties of friction welded aluminum–copper dissimilar joints

Rotary Friction Welding (RFW) is a solid-state joining technique well-suited for dissimilar metals such as aluminum and copper, despite challenges related to differences in electrochemical potential, thermal conductivity, and mechanical properties. While previous studies have explored the influence of process parameters on joint quality, limited attention has been given to the systematic optimization of axial pressure in relation to intermetallic compound (IMC) formation and mechanical performance. This study investigates the effect of varying axial pressures (20, 30, and 40 kg/cm²) on the microstructure and mechanical behavior of rotary friction-welded joints between 6061 aluminum and pure copper. The welding parameters, including rotational speed (1300 rpm), friction time (45 s), and pressure time (30 s), were held constant to isolate the effect of pressure. Macro and microstructural analyses, along with hardness and tensile testing, were conducted. The results show that axial pressure significantly influences the morphology and thickness of IMCs formed in the central weld zone (CWZ), thereby affecting joint strength. Notably, a friction pressure of 20 kg/cm² was found to be optimal, yielding the highest combination of hardness and tensile strength compared to other specimens, thus demonstrating a good balance between metallurgical bonding and mechanical performance. Compared to similar studies, this work demonstrates improved mechanical performance at a lower IMC thickness, highlighting the importance of pressure optimization in balancing metallurgical bonding with mechanical integrity. The novelty of this research lies in identifying the critical role of pressure in tailoring IMC development and optimizing joint strength for aluminum-copper dissimilar metal welding.