Magnetic properties of the Nd-Fe-B sintered magnet powders recovered by metal vapor sorption

Ken Ichi Machida, Takashi Horikawa, Masahiro Itoh

Research output: Contribution to journalArticlepeer-review

Abstract

Fine ground powders of Nd-Fe-B sintered magnets (particle size=46 ∼ 125 μm in diameter) were coated and alloyed with Zn, Mg or Yb metal by sorbing them. For the sorption of Zn or Mg metal vapor, any effective recovery of magnetic properties of the ground powders was not observed. On the contrary, a significant recovery of the decreased magnetic properties of the ground powders was observed when the Yb metal was used as a sorbing material. The sorbing temperature and time for Yb metal vapor were optimized and after heating at 800°C for 90min and annealing subsequently at 610°C for 60 min, the remanence (Br), coercivity (HcJ) and maximum energy product ((BH)max) values were increased to be 0.98 T, 712kA/m and 173 kJ/m3, respectively. From the microstructural characterizations of resulting samples, it was found that the sorbed Yb metal uniformly covered the surface and diffused to the grain boundary of fine powders forming a (Nd,Yb)Fe2 phase. The Yb metal repairs the surface defects produced by grinding and oxidation. In addition, the surface of ground powders becomes smooth through the Yb metal sorption, so that the HkHc value was improved.

Original languageEnglish
Pages (from-to)149-156
Number of pages8
JournalFuntai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy
Volume51
Issue number3
DOIs
Publication statusPublished - 2004 Mar

Keywords

  • Magnetic properties
  • Metal vapor sorption
  • Rare earth magnets
  • Recovery

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