Magnetic-Field-Assisted Directed Energy Deposition Processing of Alnico for Enhanced Coercivity and Magnetic Anisotropy

This work reports the first demonstration of in situ magnetic-field-assisted Directed Energy Deposition (DED) for fab-ricating phase-separated Alnico permanent magnets. A custom Halbach array of N52 NdFeB magnets generated anin-plane magnetic flux density of ∼1250 G during deposition, influencing melt-pool convection and solidification. Us-ing optimized DED parameters (1000 W laser power, 450 mm/s scan speed, 300 μm layer thickness), both cuboid andring-shaped geometries were produced. Field-assisted cuboids exhibited distinct dogbone morphologies attributed tomagnetohydrodynamic flow, while ring geometries showed enhanced dimensional uniformity and improved phase ho-mogeneity. X-ray diffraction confirmed suppression of spinodal decomposition in the as-processed state and formationof α1 (Fe-Co-rich) and α2 (Ni-Al-rich) phases after heat treatment. Magnetometry revealed improved coercivity andmagnetic anisotropy in field-assisted samples, achieving an energy product of (BH)max = 0.53 MGOe. These find-ings establish magnetic-field-assisted DED as a scalable pathway for engineering the microstructure of nanocompositemagnetic materials.