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 µ₀H_c = 1.16 T, remanence J_r = 0.58 T and maximum energy density of (BH)_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.

The novel quaternary compound Fe_11–xCo_x TiCe (x = 0 to 3.25) of Mn₁₂Th structure has been fabricated by arc melting. The analysis is focused on temperature dependent determination of intrinsic properties from 4 K to 750 K using domain pattern analysis and magnetometry. Above room temperature RT maximum values of anisotropy constant K₁ and saturation polarization J_s are observed for a Co content of 15 at% (x = 1.95) with K₁ and J_s of 2.15 MJ/m³ (1.22 MJ/m³) and 1.27 T (1.05 T) at RT (200 °C). At operating temperatures of 100 °C for this material magnetic properties (BH)_max= 282 kJ/m³, µ₀H_c = 0.94 T are expected. If a suitable microstructure could be processed, based on intrinsic properties of the phases the costs would be 35% per J/m³ of the costs of Dy-free Fe–Nd–B. (© 2014 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

Permanent magnets based on FePrCuB were realized on a laboratory scale through additive manufacturing (laser powder bed fusion, L-PBF) and book mold casting (reference). A well-adjusted two-stage heat treatment of the as-cast/as-printed FePrCuB alloys produces hard magnetic properties without the need for subsequent powder metallurgical processing. This resulted in a coercivity of 0.67 T, remanence of 0.67 T and maximum energy density of 69.8 kJ/m³ for the printed parts. While the annealed book-mold-cast FePrCuB alloys are easy-plane permanent magnets (BMC magnet), the printed magnets are characterized by a distinct, predominantly directional microstructure that originated from the AM process and was further refined during heat treatment. Due to the higher degree of texturing, the L-PBF magnet has a 26% higher remanence compared to the identically annealed BMC magnet of the same composition.

The TM₁₄RE₂B-based phases (TM = transition metal, RE = rare earth metal; hereafter called 14:2:1) enable permanent magnets with outstanding magnetic properties. Novel chemical compositions that represent new 14:2:1 phases necessitate that they do not demagnetize at application-specific operating temperatures. Therefore, an accurate knowledge of the Curie temperature (T_c) is important. For magnetic 14:2:1 phases, we present a machine learning model that predicts T_c by using merely chemical compositional features. Hyperparameter tuning on bagging and boosting models, as well as averaging predictions from individual models using the voting regressor, enables a low mean-absolute-error of 16 K on an unseen test set. The training set and a test set have been constructed by randomly splitting, in an 80:20 ratio, of a database that contains 449 phases (270 compositionally unique) mapped with their T_c, taken from distinct publications. The model correctly identifies the relative importance of key substitutional elements that influence T_c, especially in an Fe base such as Co, Mn, and Al. This paper is expected to serve as a basis for accurate Curie temperature predictions in the sought-after 14:2:1 permanent magnet family, particularly for transition metal substitution of within 20% in an Fe or Co base.