Mechanical characterization and numerical analysis of aluminum-copper friction welds in a geometry dependent study

Reliable aluminum-copper connections are essential for electrical conductor applications, particularly in the e-mobility sector, where lightweight conductors with high electrical conductivity and mechanical strength are required. The joining of aluminum and copper is challenging due to their differing material characteristics and the formation of brittle intermetallic compounds (IMCs) at elevated temperatures. Rotary friction welding (RFW) represents a promising solid-state joining process, as it limits heat input and IMC growth, enabling reliable dissimilar joints. In this study, aluminum-copper joints were fabricated from round bars using an industrial-scale RFW process. Cylindrical and square tensile specimens were extracted to investigate the influence of specimen geometry on mechanical response. While previous studies predominantly focused on cylindrical specimen geometries, the present work extends the investigation to square specimens in order to evaluate geometry-dependent effects on stress distribution and failure behavior. Finite element simulations analyzed geometry-induced stress distributions and stress concentrations in the dissimilar aluminum-copper material combination. In addition, electrical characterization by resistivity measurements assessed the electrical performance of the welded joints. The experimental results reveal geometry-dependent differences in the mechanical response and failure behavior. The numerical analyses capture these differences by revealing localized stress concentrations and reproduce the experimentally observed tensile stress-strain behavior. The resistivity measurements demonstrate excellent electrical conductivity of the rotary friction welded joints. The results highlight the role of specimen geometry in the failure behavior of aluminum-copper RFW joints and demonstrate their suitability for mechanically robust and electrically efficient applications in the e-mobility sector.