Microstructure and temperature dependent of coercivity of hot-deformed Nd-Fe-B magnets diffusion processed with Pr-Cu alloy

H. Sepehri-Amin, Lihua Liu, T. Ohkubo, M. Yano, T. Shoji, A. Kato, T. Schrefl, K. Hono

Research output: Contribution to journalArticlepeer-review

98 Citations (Scopus)

Abstract

The coercivity of hot-deformed Nd-Fe-B magnet was substantially enhanced from 1.0 T to 2.6 T by the grain boundary diffusion process using Pr-Cu alloy. However, the temperature dependence of coercivity is larger compared to the sample diffusion processed with Nd-Cu. Microstructure studies showed a good isolation of platelet shaped Nd2Fe14B grains by Pr-rich intergranular phase, which explains pronounced coercivity at room temperature. Small portions of Nd2Fe14B become (Nd,Pr)2Fe14B phase, which has a higher anisotropy field compared to that of the Nd2Fe14B phase at room temperature, while it becomes lower than that of the Nd2Fe14B phase above ∼110 °C. Co is depleted from the (Nd,Pr)2Fe14B phase, which is considered to cause a slight decrease in Curie temperature. Micromagnetic simulations with the magnetically isolated grains including (Nd,Pr)2Fe14B regions showed that the degradation of thermal stability of coercivity in the Pr-Cu diffusion processed sample is due to the large temperature dependence of anisotropy field in the (Nd,Pr)2Fe14B regions.

Original languageEnglish
Pages (from-to)297-306
Number of pages10
JournalActa Materialia
Volume99
DOIs
Publication statusPublished - 2015 Oct 15
Externally publishedYes

Keywords

  • Coercivity
  • Magnetic anisotropy field
  • Microstructure
  • Nd-Fe-B hot-deformed magnets

ASJC Scopus subject areas

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

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