Optimization of novel coil structure parameters for controlling Al/Fe magnetic pulse welding process

Magnetic pulse welding (MPW) for dissimilar sheet metals holds significant industrial potential as an environmentally friendly and efficient method. The process and results of MPW are highly dependent on the discharge parameters of MPW equipment. However, the development of excellent performance equipment is challenging and costly, limiting the widespread industrial application of MPW. A novel coil with the capability of amplifying current is proposed in this study, thereby mitigating the stringent requirements on MPW equipment. Firstly, the theoretical model was established to assess the effect of coil structure parameters on RLC (resistance, inductance, and capacitance) within the MPW discharge system and the magnetic pressure exerted on the sheet metal. Subsequently, numerical simulations were employed to investigate the variation trends of current density, Lorentz force, and collision parameters of the flyer sheet basing on different coil structures during the MPW process. Given that coil with 4 turns, diameter of 200 mm and pitch of 30 mm achieves a 3.1 times current amplification and a collision speed of 383.7 m/s of the flyer sheet at 9.8 kJ, while maintaining certain structural stability, the experiments were conducted. Experimental results confirmed that the small error in numerical simulation results. The metallurgical welding features, including the waveform interface, amorphous layer, and element diffusion, were observed at the 1060-DP450 weld interface achieved at 9.8 kJ. Nanoindentation results indicated that work hardening caused a higher hardness (max: 1.808 GPa) near the interface. Mechanical testing of joints welded at different energy levels (6.05-9.8 kJ) revealed that when the discharge energy exceeded 8.45 kJ, the fracture location of the joint occurs in the 1060 rather than the welding area, which is lower than the energy requirement for welding sheets of similar strength levels using traditional coils. Therefore, the novel coil structure proposed in this study reduces the difficulty of the MPW process while ensuring excellent joint performance, which is beneficial for the further industrial application of MPW technology.