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 fabricating phase-separated Alnico permanent magnets. A custom Halbach array of N52 NdFeB magnets generated an in-plane magnetic flux density of ∼1250 G during deposition, influencing melt-pool convection and solidification. Using optimized DED parameters (1000 W laser power, 450 mm/s scan speed, 300 μm layer thickness), both cuboid and ring-shaped geometries were produced. Field-assisted cuboids exhibited distinct dogbone morphologies attributed to magnetohydrodynamic flow, while ring geometries showed enhanced dimensional uniformity and improved phase homogeneity. X-ray diffraction confirmed suppression of spinodal decomposition in the as-processed state and formation of α1 (Fe–Co–rich) and α2 (Ni–Al–rich) phases after heat treatment. Magnetometry revealed improved coercivity and magnetic anisotropy in field-assisted samples, achieving an energy product of (BH)max = 0.53 MGOe. These findings establish magnetic-field-assisted DED as a scalable pathway for engineering the microstructure of nanocomposite magnetic materials.