Dissimilar welding of aluminum (Al) and copper (Cu) is a challenging endeavor due to the formation of detrimental intermetallic compounds (IMCs), among other issues. This study explores the effects of cold rolling (CR) with rolling reductions of 30 and 60% on the performance of friction stir welded Al/Cu joints. Microstructural studies revealed that brittle IMCs formed surrounding the joint interface. The IMCs with the composition of Al3Cu4, Al2Cu3, and Al3Cu precipitated close to the joint interface of Cu/Al friction stir weld, identified by x-ray diffraction and scanning electron microscopy. The tensile test also indicated that the strength of Al/Cu friction stir weld increased, while its elongation decreased by applying the rolling reductions of 30 and 60%, as compared to the as-welded condition. Both strength and elongation of Al/Cu joint were lessened by performing a rolling reduction of 60% compared to rolling reduction of 30%. Moreover, the strength–elongation balance of Al/Cu joint would be reduced by post-weld CR process, arising from lowering elongation. Strain hardening, thickness of IMCs layer, joint area of Al/Cu weld, and cracking of IMCs were significant mechanisms, which governed the mechanical behavior of cold-rolled dissimilar Al/Cu joints. In general, post-weld CR process could be useful to tensile strength in comparison with as-welded condition. Numerical simulations demonstrated strain hardening and asymmetric stress distributions in the joint interface of Al/Cu as the CR process was done, highlighting serious susceptibility of joint interface to cracking during post-weld CR process and crack propagation during tensile loading. Based on the fracture analysis, the failure site was at the Al side and joint interface for the non-deformed joint and deformed joints, respectively. The cracked IMCs were observable in the fracture surface of coldrolled friction stir welds of Al/Cu at both Al and Cu sides. This work can provide insights into optimizing the joining and CR processes for improving the properties of dissimilar welds, offering potential applications in various industries.
