Investigations on laser welding of dissimilar joints of steel and aluminum using a high-power diode laser

Lightweight construction is currently of high interest, not only for the automotive sector, but also for the maritime industry, due to various benefits. On the one hand, CO2 emissions can be reduced as a result of lower fuel consumption, and on the other hand a higher speed can be achieved, especially for yachts. Hence, hybrid joints of steel and aluminum parts are in great demand for yachts. Presently, these parts are joined using explosive welding adapters, which are complex, time-consuming, and costly to manufacture. For efficient manufacturing of such adapters, a high-power laser welding process is predestined. Aluminum alloy EN AW-6082 (t = 8 mm) and steel S355 (t = 5 mm) are welded in a lap joint configuration using a diode laser with a laser beam power of 10.4 kW. The challenge of welding this dissimilar material combination is the formation of hard and brittle intermetallic compounds within the weld seam, which may lead to cracks and negative effects on mechanical properties of the joint. To meet the required mechanical properties, the mixing ratio of the intermetallic compounds can be limited, as determined in the context of the presented welding process development. Using suitable mixing ratios, the weld seam quality can be increased as shown in metallography analysis, hardness tests, and tensile shear tests. Among other things, the welded samples provide a shear force of approximately 9 kN.