Reducing porosity and quality enhancement in keyhole laser welding under 3D configurable external magnetic field stimulation

The application of external static magnetic fields during laser welding is known to reduce defect rates, improve melt-pool stability and affect the microstructure of the materials processed. The penetration of the field through the entire volume of the process zone makes it a promising method to improve welding quality but it involves complex interactions between magnetic fields and different states of matter that are absent in classical welding. However, most of today’s research is focused on applications of static magnetic fields that are well elaborated, while alternating fields remain “terra-incognito” and their potential has still not been fully characterized. Fortunately, the generation of suitable alternating fields has recently become possible with the availability of appropriate commercial hardware. This study introduces a novel approach for reducing porosity in keyhole-mode laser welding using a 3D-configurable external magnetic field system capable of spatial–temporal modulation. While prior research primarily focuses on static magnetic fields, this work explores the effects of alternating (AMF) and rotating magnetic fields (RMF) with tunable direction and frequency—up to 200 Hz—on pore dynamics. Laser welding experiments on AlSi10Mg and 316L stainless steel revealed porosity reductions of up to 71 % under Bxy-200 Hz conditions. Unlike existing methods, our system dynamically responds to melt pool instabilities, enabling real-time force control via Lorentz and eddy current effects. CT analysis confirmed significant pore collapse and redistribution. Additionally, elemental mapping and metallographic analysis suggest enhanced alloy mixing and melt back-filling driven by electromagnetic stirring. We also identify a novel pore destabilization mechanism under AMF/RMF exposure, not attributed solely to Marangoni or Lorentz forces. These findings position configurable magnetic fields as a transformative tool for defect mitigation in advanced manufacturing.