Coercivity enhancement of nanocrystalline Ce-based magnets utilizing simplified one-step hot deformation process

Abstract

Nanocrystalline Ce-based rare earth (RE)–Fe–B alloys exhibit relatively good hard magnetic properties and high performance–cost ratio, but their properties deteriorate seriously after hot deformation (HD). Here, we present a simplified one-step HD process for preparing anisotropic Ce-based Ce_25.88La_2.85Y_4.56Fe_65.73B_0.98 (wt%) magnets. The precursor of nanocrystalline powders is first compacted inside a copper tube, and then the powders with the tube are deformed together to achieve magnetic anisotropy. Compared with the conventional two-step HD magnet, i.e., hot pressing followed by HD, one-step HD significantly increased the coercivity from 1.6 to 3.0 kOe, and the maximum magnetic energy product was improved from 3.7 to 4.8 MGOe. The microstructure characterization indicates that one-step HD can not only produce a more desirable microstructure, characterized by well-aligned platelet-shaped grains with reduced aspect ratio but also greatly inhibit the formation of coarse grain (CG) region. Both of them have been confirmed to be beneficial to enhancing coercivity by micromagnetic simulations. Our results thus demonstrate that the simplified one-step HD process offers a promising approach to developing high-performance anisotropic Ce-based magnets.

Graphical abstract