# High performance HREE-free hot-deformed Nd-Fe-B magnets by Nd- Cu grain boundary diffusion

https://mdr.nims.go.jp/datasets/c5a7d176-1dfc-4a6d-ab1c-09437eb1fcaa

## File

- [REPM2025_P1-1_Fujimura.pdf](https://mdr.nims.go.jp/filesets/0bf39d82-9885-4eb0-9f13-40a94338498c/download) ([Detail](https://mdr.nims.go.jp/filesets/0bf39d82-9885-4eb0-9f13-40a94338498c.md))
- [(abstract) P1-1_Figure1.jpeg](https://mdr.nims.go.jp/filesets/b8f5dd9f-2072-459d-b5d6-567d45053c5b/download) ([Detail](https://mdr.nims.go.jp/filesets/b8f5dd9f-2072-459d-b5d6-567d45053c5b.md))

## Id

c5a7d176-1dfc-4a6d-ab1c-09437eb1fcaa

## Local identifier



## Visibility

open_to_public

## State

published

## Created at

2025-08-13T08:39:43.019051Z

## Updated at

2025-08-20T03:30:57.985921Z

## Published at

2025-08-20T03:19:27.883625Z

## Doi

https://doi.org/10.48505/nims.5646

## First published url



## Date published



## Recorded date published



## Resource type

conference_poster

## Manuscript type

na

## Collection

- id: d28f086a-61aa-4bc7-bcae-5a1078cbc6c7
  identifier: https://mdr.nims.go.jp/pid/d28f086a-61aa-4bc7-bcae-5a1078cbc6c7
  title: The 28th International Workshop on Rare Earth and Future Permanent Magnets
    and Their Applications (REPM2025)

## Title

- title: High performance HREE-free hot-deformed Nd-Fe-B magnets by Nd- Cu grain boundary
    diffusion
  title_type: original
  lang: en

## Description

- description: "Nd-Fe-B magnets used in EVs require high coercivity to withstand high
    temperatures and high antimagnetic fields. One of the methods to improve the coercivity
    of hot-deformed Nd-Fe-B magnets without using heavy rare earth elements such as
    Dy and Tb is the grain boundary diffusion process using light rare earth elements
    [1], [2]. In this process, a eutectic alloy such as Nd-Cu is applied to the magnet
    surface followed by heat treatment at a low temperature of 500-700℃. This allows
    the eutectic alloy to diffuse from the surface to the interior of the magnet while
    inhibiting the growth of fine crystal grains, widening the grain boundary phase,
    weakening the magnetic interaction between the Nd2Fe14B particles resulting in
    an improvement in coercivity. Fig. 1(a) shows changes in remanence (Br) after
    Nd-Cu alloy diffusion, and Fig. 1(b) shows increases in coercivity (HcJ) from
    the base magnet. The decrease in Br due to grain boundary diffusion is constant
    regardless of HcJ of the base magnet. However, the larger the amount of increase
    in coercivity, the smaller the coercivity of the base magnet. This suggests that
    higher hard magnetic properties can be obtained by using a magnet with higher
    Br as the base magnet. Therefore, a base magnet with low RE composition is desirable.
    In this report, hot-deformed magnets with Br of 1.42 T at room temperature and
    HcJ of 553 kA/m at 150℃ and Hk/HcJ of 98% at 150℃ was used as the base magnet
    and Nd-Cu alloy was diffused into the grain boundary. The HcJ of the magnet was
    improved to 704 kA/m at 150℃ with Br of 1.39 T at room temperature without HREE.
    The Hk/HcJ is still maintained at 96% at 150℃, which is adequate for usage of
    EVs.\r\n\r\nReferences\r\n[1] H. Sepehri-Amin, T. Ohkubo, S. Nagashima, M. Yano,
    T. Shoji, A. Kato, T. Schrefl and K. Hono, Acta Mater. 61 (2013) 6622-6634\r\n[2]
    H. Sepehri-Amin, Lihua Liu, T. Ohkubo, M. Yano, T. Shoji, A. Kato, T. Schrefl,
    and K. Hono, Acta Mater. 99 (2015) 297-306"
  description_type: abstract
  lang: en

## Creator

- name: Kazumasa Fujimura
  role: author
  organization: Corporate R&D center, Daido Steel Co., Ltd., Japan
- name: Takanori Kajiwara
  role: author
  organization: Corporate R&D center, Daido Steel Co., Ltd., Japan
- name: Takashi Oikawa
  role: author
  organization: Corporate R&D center, Daido Steel Co., Ltd., Japan
- name: Hiroshi Miyawaki
  role: author
  organization: Material solution dept., Daido Steel Co., Ltd., Japan

## Contact agent



## Publisher

organization: National Institute for Materials Science (NIMS)

## Managing organization



## Keyword

- subject: REPM2025
  schema: not_defined
- subject: xEV
  schema: not_defined
- subject: Nd-Fe-B magnet
  schema: not_defined
- subject: HREE-free
  schema: not_defined
- subject: Hot-deformed magnet
  schema: not_defined
- subject: Grain boundary diffusion
  schema: not_defined

## Rights

- identifier: https://creativecommons.org/licenses/by-nc-nd/4.0/

## Other identifier(s)



## Data origin

- data_origin_type: other

## Embargo



## Journal



## Conference

name: REPM2025
start_date: 2025-07-27
end_date: 2025-07-31
identifier: https://www.nims.go.jp/mmu/repm2025/

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## Specimen



## Chemical composition



## Structure for specimen



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## Fileset

- id: 0bf39d82-9885-4eb0-9f13-40a94338498c
  filename: REPM2025_P1-1_Fujimura.pdf
  content_type: application/pdf
  size: 1691921
  md5: 074e70c474c81c6cc6b65fb70a49884c
- id: b8f5dd9f-2072-459d-b5d6-567d45053c5b
  filename: "(abstract) P1-1_Figure1.jpeg"
  content_type: image/jpeg
  size: 61936
  md5: dfab9494785be48a55ae6be37058d8a3

## Thumbnail

fileset_id: 0bf39d82-9885-4eb0-9f13-40a94338498c
filename: REPM2025_P1-1_Fujimura.pdf