R-Fe-B MICROCRYSTALLINE HIGH-DENSITY MAGNET AND PROCESS FOR PRODUCTION THEREOF

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A process for the production of an R-Fe-B microcrystalline high-density magnet which comprises preparing an R-Fe-B rare earth alloy powder having a mean particle size of less than 20μm, forming the powder into a compact, subjecting the compact to the HD step of conducting the hydrogenation and dis- proportionation of the compact by heat-treating the compact at a temperature of 550°C or above but below 1000°C in hydrogen gas and then the DR step of conducting the dehydrogenation and recombination of the resulting compact by heat-treating the resulting compact in a vacuum or inert atmosphere at a temperature of 550°C or above but below 1000°C to form a porous material which has a density of 60 to 90% of the true density and contains microcrystal grains having a mean grain size of 0.01 to 2μm, and then heat-treating the porous material in a vacuum or inert atmosphere at a temperature of 750°C or above but below 1000°C to densify the material to a density of at least 93% of the true density.