Effect of axial static magnetic field on microstructure evolution, performance, and melt pool signals of AlSi10Mg fabricated by laser powder bed fusion

Static magnetic field (SMF) assisted laser powder bed fusion (LPBF) has significant potential to improve the mechanical properties of AlSi10Mg parts. In this study, the tensile properties of AlSi10Mg are improved under the SMF, mostly due to the increased relative density and finer microstructure. Under the SMF, the epitaxial growth in the building direction is inhibited, indicating a weakening 001 texture. However, the mechanism of the magnetic field within the melt pool remains unknown. The melt pool area, temperature gradient, radiation emission, and spatter extracted by in-situ monitoring technology provide an excellent opportunity for increasing the understanding of the SMF-assisted LPBF process. The Marangoni convection in the melt pool is limited by the magnetic damping effect, which improves the melt pool and radiation stability and reduces spatters. Further, thermoelectric magnetic force at the cell surface in the mushy zone improves the local convection, increasing the thermal diffusion rate in the melt pool boundary during the solidification. This results in smaller melt pool areas, reduced radiation emission magnitude, and a steep temperature gradient. As a result, the directional solidification in the thermal diffusion direction is inhibited, and the microstructure is refined. Finally, the thermoelectric magnetic convection also facilitates the escape of the entrapped pores in the melt pool, increasing relative density.