Structural morphologies in the case of the resistance spot welding of aluminium/steel joints

In comparison with the joining of similar materials, the thermal joining of dissimilar materials such as aluminium and steel is characterised by complicated joining technologies. The parameters of the welding current and the welding time have the biggest influences on the temperature profile in the joining plane. The resulting diffusion kinetics of the principal alloying elements exert decisive influences on the forming structural morphology and thus on the mechanical and technological properties. Any arising intermetallic phases of the FexAly type make the joint more brittle because of their complex lattice structure and their bonding character. The shorttime, strong heating of the joining plane using high welding currents should be striven for in order to attain a fine-grained homogeneous nature of the intermetallic compound and to minimise the distinctness of this.