The function of disproportionation and desorption stages of hydrogenation-disproportionation-desorption-recombination (HDDR) process in the formation of magnetic anisotropy was studied. The results showed that degree of anisotropy (DOA) of Nd13Fe80B7 induced by appropriate HDDR process is comparable with that of Nd13Fe80-xB7Mx (M=Co, Zr or Ga), however, the moder-ate coercive force of Nd13Fe80B7 magnetic powder led to an undesirable (BH)max of 104 kJ/m3 in bonded magnet. Experiments demonstrated that a relatively short disproportionation time, combined with a high desorption temperature and slow desorption rate, during HDDR process is beneficial to anisotropy attainment, but HDDR Nd13Fe80B7 magnetic powder becomes isotropic if the dispropor-tionation time is longer than a certain period. This phenomenon strongly indicated that the origin of anisotropy in NdFeB-type HDDR material is contributed by disproportionation stage. XRD (X-ray Diffraction) analysis and TEM (Transmission Electron Mi-croscope) observation told that no other phase except NdH2, α-Fe and Fe2B has been found in the disproportionation step. The for-mation of HDDR Nd13Fe80B7 anisotropy might be related to the early lamella disproportionation structure.
The function of disproportionation and desorption stages of hydrogenation-disproportionation-desorption-recombination (HDDR) process in the formation of magnetic anisotropy was studied. The results showed that degree of anisotropy (DOA) of Nd13Fe80B7 induced by appropriate HDDR process is comparable with that of Nd13Fe80-xB7Mx (M=Co, Zr or Ga), however, the moder-ate coercive force of Nd13Fe80B7 magnetic powder led to an undesirable (BH)max of 104 kJ/m3 in bonded magnet. Experiments demonstrated that a relatively short disproportionation time, combined with a high desorption temperature and slow desorption rate, during HDDR process is beneficial to anisotropy attainment, but HDDR Nd13Fe80B7 magnetic powder becomes isotropic if the dispropor-tionation time is longer than a certain period. This phenomenon strongly indicated that the origin of anisotropy in NdFeB-type HDDR material is contributed by disproportionation stage. XRD (X-ray Diffraction) analysis and TEM (Transmission Electron Mi-croscope) observation told that no other phase except NdH2, α-Fe and Fe2B has been found in the disproportionation step. The for-mation of HDDR Nd13Fe80B7 anisotropy might be related to the early lamella disproportionation structure.
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