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

Acta Materialia, Volume 61, Issue 6, Pages 1982–1990, 2013

2013年1月22日(火)

H.Sepehri-Amin、T.Ohkubo、K.Hono

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.





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文部科学省

文部科学省
元素戦略プロジェクト(活動紹介)
NIMS磁石パートナーシップ

元素戦略拠点

触媒・電池元素戦略拠点
触媒・電池元素戦略研究拠点 (京都大学)
東工大元素戦略拠点
東工大元素戦略拠点 (東京工業大学)
構造材料元素戦略研究拠点
構造材料元素戦略研究拠点 (京都大学)
高効率モーター用磁性材料技術研究組合
高効率モーター用 磁性材料技術研究組合