Coercivity enhancement of anisotropic Dy-free Nd–Fe–B powders by conventional HDDR process

• Published in: Journal of magnetism and magnetic materials Vol. 324; no. 22; pp. 3723 - 3726
• Main Authors: Morimoto, K., Katayama, N., Akamine, H., Itakura, M.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-11-2012; Elsevier
• Subjects: Aluminum; Coercive force; Coercivity; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Desorption; Exact sciences and technology; Ferrous alloys; Grain boundaries; Hydrogenation–decomposition–desorption–recombination (HDDR); Magnetic materials; Magnetic properties and materials; Magnetism; Nd–Fe–B; Neodymium; Permanent magnets; Physics; Studies of specific magnetic materials; Nd–Fe–B; Grain boundaries; Permanent magnets; Hydrogenation–decomposition–desorption–recombination (HDDR); Coercivity; Scanning electron microscopy; Hydrogenation-decomposition-desorption-recombination (HDDR); Nd-Fe-B; HDDR process; Transmission electron microscopy; Anisotropy; Coercive force; Fine grain structure; Chemical composition; Iron base alloys
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2012.06.003

Coercivity enhancement of Dy-free Nd–Fe–Co–B–Ga–Zr powders was studied using the conventional hydrogenation–decomposition–desorption–recombination (HDDR) process. It was found that the addition of Al together with the proper Nd content and the slow hydrogen desorption of the HDDR treatment can induce high coercivity in the powder. For example, the 14.0at% Nd–2.0at% Al powder exhibits HcJ of 1560kA/m, Br of 1.22T, and (BH)max of 257kJ/m3. The high coercivity inducement of the powder is thought to be attributed to the formation of Nd-rich phase, which continuously surrounds fine Nd2Fe14B grains.
► The Al addition enhances coercivity of HDDR-processed Dy-free Nd–Fe–B powders. ► This might be attributed to the formation of Nd-rich grain boundary (GB) phase. ► Larger Nd contents develop the GB phase and then improve the coercivity further.