Investigation of the effects of welding parameters on laser welded joints of dissimilar high strength steel and aluminum alloys

Due to the utilizing aluminum alloys and high strength steel in hybrid components, it will become a primary target of the automotive industry to combine these types of materials with different thermal and physical properties. Intermetallic phases are formed during solidification in the melt pool formed by joining these dissimilar materials. In terms of the mechanical strength and quality of the weld, these phases should be limited and controlled. In this study, the effect of welding parameters and heat input on the mechanical and metallurgical properties of laser welded 6082-T6 aluminum alloy and DP600 high strength steel sheet was investigated. Depending on the heat input, the dimensions of the weld seam were examined with the help of optical microscope. Intermetallic phases formed in the joint were examined by micro hardness measurements and SEM-EDX analyzes. The tensile tests of the welded parts were carried out to determine the mechanical strengths and to relate them to the welding parameters. It has been seen that the most important parameters affecting the mechanical strength of the aluminum-steel joints are the welding speed and the laser power. It has been found that the heat input determined by laser power and welding speed has a great influence on the weld seam geometry and the intermetallic phases in the connection region. With increasing heat input, it was determined that the size of the melt pool and the formation of intermetallic phases increased.