Anisotropic HDDR-treated Nd-Fe-B alloy flakes for mechanically oriented composite magnets
K. Morimoto, K. Igarashi, K. Kato, R. Nakayama and M. Yagi

ABSTRACT
To explore the possibilities of producing Nd-Fe-B materials for the application of mechanically oriented composite magnets. Nd12.6Fe62.3Co17.4 Al0.6Zr0.1B7.0 alloy flakes were prepared by hydrogenation-decomposition-desorption-recombination (HDDR) -treating the melt-spun ribbons, and magnetic properties of the resin-bonded compacts made from them were examined. The as-spun ribbons of 230µm in thickness exhibit a texture with the c-axes of Nd2Fe14B grains oriented perpendicularly to the ribbon planes, and possess low coercivities (HcJ’s) of 90 kA/m. HDDR treatment can induce high HcJ’s of approximately 880kA/m in these ribbons maintaining the original crystallographic orientation. The flakes obtained by crushing the HDDR-treated ribbons can be mechanically aligned by compaction molding with no applied magnetic field. The resin-bonded compact prepared form the flakes with the highest magnetic anisotropy exhibits Br of 0.78T and (BH)max of 106kJ/m3 in the pressing direction (easy magnetization direction). When its density is density is 6.0Mg/m3 . These magnetic properties are superior to those of the isotropic resin-bonded magnets produced from the commercially available rapidly quenched Nd-Fe-B powders.
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