Laser powder bed fusion of anisotropic Nd-Fe-B bonded magnets utilizing an in-situ mechanical alignment approach

Abstract

Nd-Fe-B bonded magnets are an important class of permanent magnets, employed in many technological sectors. Additive Manufacturing (AM) enables the fabrication of net-shape bonded magnets with complex geometries, allowing to tailor their magnetic stray field specifically for a given application. A crucial challenge is the production of magnetically anisotropic components. Approaches presented in the literature up to now required a post-printing procedure or the complex integration of a magnetic field source into the AM process. Here, we present a technique to fabricate anisotropic bonded magnets via Laser Powder Bed Fusion (LPBF) by utilizing the mechanical alignment of anisotropic particles in a single step, without the need for a magnetic field source. Anisotropic bonded magnets were fabricated using a mixture of anisotropic Nd-Fe-B powder (MQA-38–14) and polyamide-12 (PA12). This magnetic powder consists of ellipsoidal particles, where the easy magnetization axis is distributed perpendicular to their longest side, and the mean aspect ratio of 3:1 can be exploited to generate magnetic texture. Depending on the particle size used as feedstock, the degree of alignment (<cosθ>) can be tailored to a maximum of <cosθ> = 0.78. The fabricated anisotropic bonded magnets exhibited a maximum remanence of Jr = 377 mT and an energy product of (BH)max = 28.6 kJ/m3, respectively.