抄録
In order to enhance the anisotropy of Nd-Fe-B HDDR treated powder, we have investigated the hydrogen pressure dependence of the recombination reaction temperature, for disproportionated Nd2Fe14B powder. The recombination pressure of hydrogen was higher than the dissociation pressure of NdH2. The addition of Co and/or Ga increases the recombination pressure. The heat treatment conditions of the disproportionation stage were found to effect the magnetic properties. The alloys disproportionated by heating from room temperature under hydrogen, exhibited high coercivities and moderate remanences, whereas those heated up to the HDDR treatment temperature (≥800°C) under vacuum, and then disproportionated by exposing to hydrogen, showed higher remanences with lower coercivities. Various heat treatment patterns were also used for the recombination stage, and it was found that heating at high temperatures under Ar, rather than in a vacuum, enhanced the remanence to give B1/Js ≈0.9, i. e. slow desorption with a relatively high partial pressure of hydrogen, is more effective in producing anisotropic HDDR powder.
