Microstructure and Magnetic Properties of Gas Atomized Powders of Mixed Rare Earth Iron Boron

摘要

Novel mixed rare earth iron boron (MRE_2Fe_(14)B) permanent magnet alloys have the desirable ability to be gas atomized into powders with competitive magnetic properties. Current stoichiometric Nd_2Fe_(14)B permanent magnets (having high flux density) are typically melt-spun to achieve the cooling rates necessary to create the amorphous or nanocrystalline phases desired for permanent magnets. Gas atomized powders have a spherical shape which is preferred for polymer bonded magnets as compared to the flake geometry of melt-spun powder. The most beneficial magnetic property of MRE_2Fe_(14)B is the stabilization of coercivity, remenance and therefore energy product (BH_(amx)) over a range of elevated operating temperatures (>150℃). With the use of glass formers the microstructure can be modified creating a fine dendritic structure, microcrystalline structure, and amorphous structure depending on particle size. Similar to flake particulate, as-atomized powders often need annealing treatments to modify the microstructure for optimal magnetic properties.