Preparation of ultraf ine jet-milled powders for Nd-Fe-B sintered magnets using hydrogenation-disproportionation-desorption-recombination and hydrogen decrepitation processes

摘要

Dy addition is used to increase the coercivity of Nd-Fe-B sintered magnets. Given that Dy is rare and expensive, a method is needed for reducing the Dy content in such magnets without decreasing their coercivity. Refining Nd_2Fei_4B grains is a prospective method for increasing the coercivity of Nd-Fe-B magnets. Conventional jet milling, however, cannot crush strip-casted Nd-Fe-B alloys into powders less than 1 μm in size. We report a process for preparing ultrafine jet-milled powders with an average size of 0.33 μm for Nd-Fe-B sintered magnets: a combination of hydrogenation-disproportionation-desorption-recombination, hydrogen decrepitation, and He jet milling.