Analysis on interface characteristics and metal particle distributions in electromagnetic pulse welding with aluminum to steel

In order to investigate the effect of metal particle movement on interface connection performance in electromagnetic pulse welding of aluminum to steel, based on the formation mechanism of metal particles, the interfacial structure and tensile shear strength were analyzed. The results showed that metal particle entrapment at the interface caused local melting of aluminum. Steel particles generated in situ FeAl, forming an unbonded zone. Along the welding direction, the impact effect of the separate jet on the aluminum plate gradually increased, forming a metallurgical bond, accompanied by aluminum-rich intermetallic phases. FeAl + Fe₂Al₅ existed in the straight seam. Fe₂Al₅ + FeAl₃ existed in the corrugated zone. FeAl + FeAl₃ existed in the large corrugated zone. The transition zone of the welding interface was formed by plastic deformation of aluminum pressed into the steel. There were steel particles on the outer side of the aluminum plate weld, while there were molten aluminum carrying steel particles at the steel plate weld, mainly composed of FeAl + Fe₂Al₅ + FeAl₃. A large number of metal particles gathered on the inner side of the weld and were distributed in the form of elliptical rings. Metal particles remained on the surface of the aluminum plate, causing pits, but there were embedded sheets of aluminum on the surface of the steel plate. Therefore, locations where metal particles were trapped and more intermetallic compounds were produced became shear fracture sources. The wavelength formula was used to adjust the lap gap to reduce particle entrapment, breaking the elliptic weld at the aluminum, and improving joint strength.