Anisotropic HDDR-treated Nd-Fe-B alloy flakes for mechanically oriented composite magnets

To explore the possibilities of producing Nd-Fe-B materials for the application of mechanically oriented composite magnets, Nd12.6Fe62.3Co17.4Al0.6Zr0.1B7.0 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 230 μm 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 880 kA/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 from the flakes with the highest magnetic anisotropy exhibits Br of 0.78 T and (BH)max of 106 kJ/m3 in the pressing direction (easy magnetization direction), when its density is 6.0 Mg/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.