Laser lap welding of zinc-coated steel and 6016 aluminum alloy with Pb interlayer

The laser lap welding experiment with the Pb interlayer was carried out based on the DC56D + ZF galvanized steel of 1.2 mm and the 6016 aluminum alloy of 1.15 mm. The best appearance of welding were obtained by adjusting the welding parameters. By using optical microscopy, scanning electron microscopy, X-ray diffraction and the tensile test, mechanical properties of joints, fracture morphology and the main phase of the welded joint regional was studied. The results showed that when Pb interlayer was added in steel/aluminum, the average tensile strength and elongation of the steel/aluminum laser welding joints were 68.51 MPa and 2.37% respectively. Compared with that without Pb interlayer, the strength and alongation were improved significantly. The element distribution, phase composition and microstructure of the steel/aluminum interface were changed by the addtion of Pb interlayer. In the transition region of steel/aluminum joints, Fe, Al, Zn, Mg, Pb elements of the mixing zone width was larger, and a new ductile intermetallic compounds-Mg₂Pb was produced, which could improve the mechanical properties of weld metal.