Parameter optimization of laser welding of steel to Al with pre-placed metal powders using the Taguchi-response surface method

Abstract

Welding of steel to aluminum alloy is a difficult work due to the formation of brittle intermetallic compounds. In order to improve the quality of the dissimilar materials weld joints, metal powders are pre-placed on the surface of aluminum alloy prior to welding. In this study, laser welding technique is employed to join DC04 steel to 6016 aluminum alloy with pre-placed metal powders in a lap joint configuration. The morphology, micro-structure and elemental composition of the joints are characterized using SEM equipped with an EDS and optical micro-scope while the micro-hardness and tensile strength are measured. It is indicated that although metal powders do not form compounds directly with Fe or Al, they prevent the contact of Fe and Al. Tensile experiments show that the pre-placed metal powders can significantly improve the joints’ tensile properties. The combined Taguchi-response surface method approach is employed to optimize the laser welding parameters and the optimal condition to have a quality weld is found at laser power 1344.73 W, welding speed 30 mm/s, Defocus distance −2 mm, Shield gas flow 30 L/min. Confirmation experiment proves that the Taguchi-response surface method is an effective way to optimize welding parameters to gain higher mechanical resistance reach to 165.24 N/mm and the bead appearance of optimization joint with fish scales and without cracks.