Effect of additional underneath magnetic field on joining mechanism of aluminum alloy to galvanized steel joints in pulsed current gas metal arc welding

In joining of aluminum alloy to steel by pulsed current gas metal arc welding (GMAW) process, drastic input of heat energy from the arc heat source causes an excessive growth of brittle Fe-Al intermetallics layer and blow holes. In this study, application of additional underneath magnetic field (B) to GMAW was attempted to clarify the effect of controlled Lorentz force on heat input, joining mechanism, and Fe-Al IMC growth at the joint interface. 1.2 mm thick AA5052 aluminum alloy and hot-dip galvanized steel were joined in lap configuration by varying the B direction to control the Lorentz force. Arc phenomenon and weld pool flow, macroscopic and microscopic observation of the joints, and corresponding tensile-shear strength of the joints were investigated to understand the joining mechanism. It was found that the additional underneath Lorentz force to the rear side oscillated the arc to the steel side depending on the welding current and decreased the energy density to the base metal. Further, the Lorentz force transformed bead formation and suppressed IMC layer growth with showing the maximum tensile-shear strength as 187 MPa.