Coercivity enhancement by grain refinement for anisotropic Nd2Fe14B-type magnetic powders

Anisotropic Nd-Fe-B magnetic powders with high coercivity of 1440 kA/m as well as maximum energy products of 296 kJ/m(3) were prepared. It was clearly observed that hydrogenation disproportionation desorption recombination (HDDR) process was confined in single crystal particles of Nd-Fe-B alloys. The recombined grains can be refined from 400 to 250 nm. The grain size refinement leads to a coercivity enhancement from 920 to 1440 kA/m. The coercivity enhancement is related to the grain refinement and the resultant formation of uniform Nd-rich grain boundary as strong pinning sites. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.National Natural Science Foundation of China [51271004, 51371009, 51171001]; Foundation of Key Laboratory of Neutron Physics of CAEP [2014BB02]SCI(E)EIARTICLEhanjingzhi@pku.edu.cn; jbyang@pku.edu.cn57-6011