Study on Ultrafine-Grained Sintered Nd–Fe–B Magnets Produced From Jet-Milled HDDR Powders

摘要

Ultrafine-grained sintered Nd–Fe–B magnets were produced from jet-milled hydrogenation–disproportionation–desorption–recombination powders in a proper sintering condition. The coercivity of kOe was obtained by sintering below 950 °C, and the average grain size was . For the newly fine-grained magnets, a higher magnetic field is needed to magnetize them, giving rise to a two-step initial magnetization curve involving domain wall pinning at the grain boundary phase. Microstructure observation indicated that the Nd-rich phases did not encapsulate the 2:14:1 phases effectively, resulting in defects and interactions between adjacent 2:14:1 grains, which are responsible for the relatively low coercivity of the fine-grained magnets.