Joining of functionally adapted and weight-optimized semi-finished parts by electromagnetic compression is investigated taking into account that the resulting component is further processed by hydroforming. For this purpose both ends of an aluminum tube are connected to steel tubes. During the subsequent hydroforming of the hybrid tube the joints are exposed to extreme loading. Finite-Element-Simulation is applied for characterizing and quantifying these loads. The electromagnetic joining process is analyzed, the joints are characterized by microstructural analysis and the resulting properties of the joint are evaluated by model experiments