Distribution of Dy in high-coercivity (Nd,Dy)-Fe-B sintered magnet

W. F. Li; H. Sepehri-Amin; T. Ohkubo; N. Hase; K. Hono

doi:10.1016/j.actamat.2011.01.046

Distribution of Dy in high-coercivity (Nd,Dy)-Fe-B sintered magnet

W. F. Li, H. Sepehri-Amin, T. Ohkubo, N. Hase, K. Hono

Research output: Contribution to journal › Article › peer-review

98 Citations (Scopus)

Abstract

The enhanced coercivity of Dy-substituted Nd-Fe-B-based sintered magnets is generally believed to be due to the enhanced magnetocrystalline anisotropy of the compound (Nd,Dy)₂Fe₁₄B. In this work we have analyzed the distribution of Dy in sintered (Nd,Dy)-Fe-B magnets using the three-dimensional atom probe (3DAP) technique complemented with high-resolution scanning and transmission electron microscopy. We found Dy atoms are not uniformly distributed throughout the microstructure but some Dy oxides are present. 3DAP results revealed that a nearly pure Nd layer of about 6 nm is present at some of the interfaces between the (Nd,Dy)-rich phase and the (Nd,Dy)₂Fe₁₄B phase. Like other optimally annealed sintered magnets, a thin Nd- and Cu-enriched layer was found throughout grain boundaries, in which Dy was not enriched compared with the surrounding area. Based on these newly found microstructural features, the coercivity of (Nd,Dy)-Fe-B sintered magnets is discussed.

Original language	English
Pages (from-to)	3061-3069
Number of pages	9
Journal	Acta Materialia
Volume	59
Issue number	8
DOIs	https://doi.org/10.1016/j.actamat.2011.01.046
Publication status	Published - 2011 May
Externally published	Yes

Keywords

Atom probe
Coercivity
Grain boundaries
Hard magnets
Nd-Fe-B

ASJC Scopus subject areas

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

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10.1016/j.actamat.2011.01.046

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title = "Distribution of Dy in high-coercivity (Nd,Dy)-Fe-B sintered magnet",

abstract = "The enhanced coercivity of Dy-substituted Nd-Fe-B-based sintered magnets is generally believed to be due to the enhanced magnetocrystalline anisotropy of the compound (Nd,Dy)2Fe14B. In this work we have analyzed the distribution of Dy in sintered (Nd,Dy)-Fe-B magnets using the three-dimensional atom probe (3DAP) technique complemented with high-resolution scanning and transmission electron microscopy. We found Dy atoms are not uniformly distributed throughout the microstructure but some Dy oxides are present. 3DAP results revealed that a nearly pure Nd layer of about 6 nm is present at some of the interfaces between the (Nd,Dy)-rich phase and the (Nd,Dy)2Fe14B phase. Like other optimally annealed sintered magnets, a thin Nd- and Cu-enriched layer was found throughout grain boundaries, in which Dy was not enriched compared with the surrounding area. Based on these newly found microstructural features, the coercivity of (Nd,Dy)-Fe-B sintered magnets is discussed.",

keywords = "Atom probe, Coercivity, Grain boundaries, Hard magnets, Nd-Fe-B",

author = "Li, {W. F.} and H. Sepehri-Amin and T. Ohkubo and N. Hase and K. Hono",

note = "Funding Information: This work was in part supported by CREST-JST, the Rare Metal Substitute Materials Development Project on the development of technology for reducing dysprosium usage in a rare-earth magnet, NEDO, World Premier International Research Center Initiative (WPI Initiative) on Materials Nanoarchitronics, MEXT, Japan. We acknowledge A. Manabe and A. Kato at Toyota for the provision of the experimental samples. H. Sepehri-Amin and N. Hase acknowledge NIMS for the provision of a NIMS Junior Research Assistantship.",

year = "2011",

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doi = "10.1016/j.actamat.2011.01.046",

language = "English",

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T1 - Distribution of Dy in high-coercivity (Nd,Dy)-Fe-B sintered magnet

AU - Li, W. F.

AU - Sepehri-Amin, H.

AU - Ohkubo, T.

AU - Hase, N.

AU - Hono, K.

N1 - Funding Information: This work was in part supported by CREST-JST, the Rare Metal Substitute Materials Development Project on the development of technology for reducing dysprosium usage in a rare-earth magnet, NEDO, World Premier International Research Center Initiative (WPI Initiative) on Materials Nanoarchitronics, MEXT, Japan. We acknowledge A. Manabe and A. Kato at Toyota for the provision of the experimental samples. H. Sepehri-Amin and N. Hase acknowledge NIMS for the provision of a NIMS Junior Research Assistantship.

PY - 2011/5

Y1 - 2011/5

N2 - The enhanced coercivity of Dy-substituted Nd-Fe-B-based sintered magnets is generally believed to be due to the enhanced magnetocrystalline anisotropy of the compound (Nd,Dy)2Fe14B. In this work we have analyzed the distribution of Dy in sintered (Nd,Dy)-Fe-B magnets using the three-dimensional atom probe (3DAP) technique complemented with high-resolution scanning and transmission electron microscopy. We found Dy atoms are not uniformly distributed throughout the microstructure but some Dy oxides are present. 3DAP results revealed that a nearly pure Nd layer of about 6 nm is present at some of the interfaces between the (Nd,Dy)-rich phase and the (Nd,Dy)2Fe14B phase. Like other optimally annealed sintered magnets, a thin Nd- and Cu-enriched layer was found throughout grain boundaries, in which Dy was not enriched compared with the surrounding area. Based on these newly found microstructural features, the coercivity of (Nd,Dy)-Fe-B sintered magnets is discussed.

AB - The enhanced coercivity of Dy-substituted Nd-Fe-B-based sintered magnets is generally believed to be due to the enhanced magnetocrystalline anisotropy of the compound (Nd,Dy)2Fe14B. In this work we have analyzed the distribution of Dy in sintered (Nd,Dy)-Fe-B magnets using the three-dimensional atom probe (3DAP) technique complemented with high-resolution scanning and transmission electron microscopy. We found Dy atoms are not uniformly distributed throughout the microstructure but some Dy oxides are present. 3DAP results revealed that a nearly pure Nd layer of about 6 nm is present at some of the interfaces between the (Nd,Dy)-rich phase and the (Nd,Dy)2Fe14B phase. Like other optimally annealed sintered magnets, a thin Nd- and Cu-enriched layer was found throughout grain boundaries, in which Dy was not enriched compared with the surrounding area. Based on these newly found microstructural features, the coercivity of (Nd,Dy)-Fe-B sintered magnets is discussed.

KW - Atom probe

KW - Coercivity

KW - Grain boundaries

KW - Hard magnets

KW - Nd-Fe-B

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Distribution of Dy in high-coercivity (Nd,Dy)-Fe-B sintered magnet

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