Additive Manufacturing of Bulk Nanocrystalline FeNdB Based Permanent Magnets

• Main Authors: Dagmar Goll, Felix Trauter, Timo Bernthaler, Jochen Schanz, Harald Riegel, Gerhard Schneider
• Format: Article
• Language: English
• Published: MDPI AG 2021-05-01
• Series: Micromachines
• Subjects: additive manufacturing; NdFeB; selective laser melting (SLM); laser powder bed fusion (L-PBF); coercivity; nanocrystalline magnets
• Online Access: https://www.mdpi.com/2072-666X/12/5/538

Lab scale additive manufacturing of Fe-Nd-B based powders was performed to realize bulk nanocrystalline Fe-Nd-B based permanent magnets. For fabrication a special inert gas process chamber for laser powder bed fusion was used. Inspired by the nanocrystalline ribbon structures, well-known from melt-spinning, the concept was successfully transferred to the additive manufactured parts. For example, for Nd16.5-Pr1.5-Zr2.6-Ti2.5-Co2.2-Fe65.9-B8.8 (excess rare earth (RE) = Nd, Pr; the amount of additives was chosen following Magnequench (MQ) powder composition) a maximum coercivity of <i>µ</i>₀<i>H</i>_c = 1.16 T, remanence <i>J</i>_r = 0.58 T and maximum energy density of (<i>BH</i>)_max = 62.3 kJ/m³ have been achieved. The most important prerequisite to develop nanocrystalline printed parts with good magnetic properties is to enable rapid solidification during selective laser melting. This is made possible by a shallow melt pool during laser melting. Melt pool depths as low as 20 to 40 µm have been achieved. The printed bulk nanocrystalline Fe-Nd-B based permanent magnets have the potential to realize magnets known so far as polymer bonded magnets without polymer.