Numerical simulation and experimental analysis of weld forming in aluminum/steel electromagnetic pulse welding

To clarify the weld forming process of aluminum/steel electromagnetic pulse welding (EMPW), the collision process between the 6061 aluminum alloy flyer plate and the 304 stainless steel plate was simulated by using the Ansys Maxwell finite element and loading an external circuit, and Vickers hardness, electron back scatter diffraction (EBSD), and X-ray diffraction analysis (XRD) tests were conducted. The results indicate that the simulation results of the electromagnetic force distribution law, the aluminum plate rebound process, and the weld morphology are consistent with the experimental data. The induced current density determines the contour characteristics of the weld, which is mainly concentrated on the lower surface of the aluminum plate above the middle beam of the coil, follows a normal distribution with a maximum value of 17.7 × 10⁹ A/m2, and presents symmetrical rectangular loop characteristics. A strong magnetic field concentration effect exists at the overlap and boundary of the aluminum plate. The electromagnetic force density directly opposite the aluminum plate on the middle beam is the highest, reaching 27.3 × 10¹⁰ N/m³, which causes an instantaneous rebound upon colliding with the steel plate and fails to achieve welding. Under the action of magnetic field concentration, the microstructure at the stainless steel weld transforms from face-centered cubic (FCC) to body-centered cubic (BCC). Furthermore, within the electromagnetic force density range for weld formation, a greater electromagnetic force density leads to a larger transformation amount and more obvious hardness strengthening. The research results provide a data reference for reducing the rebound area, increasing the weld area, and improving the joint strength.