MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
Evaluation of the Microstructural Contribution to the Coercivity of Fine-Grained Nd–Fe–B Sintered Magnets
Togo FukadaMasashi MatsuuraRyota GotoNobuki TezukaSatoshi SugimotoYasuhiro UneMasato Sagawa
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2012 Volume 53 Issue 11 Pages 1967-1971

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Abstract

The relationship between coercivity and the microstructural parameters α and Neff for grain refined Nd–Fe–B sintered magnets was examined. The parameter α describes the effect of grain misalignment and a decrease in the magnetocrystalline anisotropy of the Nd2Fe14B grains on the coercivity. The parameter Neff describes the influence of the demagnetizing field on the coercivity. These parameters were evaluated for Nd–Fe–B sintered magnets with three different grain sizes and the same composition. Neff decreased with grain refinement, while α varied only slightly with grain size. This implies that the decrease in the demagnetizing field increased the coercivity through grain refinement. Grain shape and asperity were then evaluated by the aspect ratio, angle of the grain to the direction of magnetization, and reverse circularity. Although the aspect ratio and angle of the grains were not related to the changes in Neff, variation of the average reverse circularity corresponded to the changes in Neff with grain refinement. Therefore, improving the asperity should increase the coercivity through grain refinement.

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© 2012 The Japan Institute of Metals and Materials
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