The mechanism of coercivity enhancement by the grain boundary diffusion process of Nd-Fe-B sintered magnets

H. Sepehri-Amin, T. Ohkubo, K. Hono

Research output: Contribution to journalArticle

133 Citations (Scopus)

Abstract

We discuss the mechanism of the coercivity enhancement by the grain boundary diffusion process (GBDP) using Dy vapor based on detailed microstructural characterizations. Scanning electron microscopy and electron probe microanalysis showed that a (Nd,Dy)2Fe14B shell formed in the outer region of Nd2Fe14B grains while its thickness decreased from the surface to the center of a cube-shaped sample. Atom probe tomography showed that the Dy content at grain boundaries (GBs) was close to that in the (Nd,Dy)2Fe14B shell. High-temperature annealing (at 900 °C) of a GB diffusion processed magnet led to the disappearance of the GB layers, which resulted in a substantial reduction in coercivity. This suggests that both the (Nd,Dy)2Fe14B shell and the Nd-rich GB phase layer are required microstructural features for the coercivity enhancement by the GBDP.

Original languageEnglish
Pages (from-to)1982-1990
Number of pages9
JournalActa Materialia
Volume61
Issue number6
DOIs
Publication statusPublished - 2013 Apr 1
Externally publishedYes

Keywords

  • Coercivity
  • Grain boundary
  • Grain boundary diffusion process
  • Nd-Fe-B
  • Permanent magnets

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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