Abstract
The development of high-performance Nd–Dy–Fe–B magnets that minimise the consumption of the scarce rare earth (RE) element Dy remains a major global scientific and technological quest. Here, we designed an alloy microstructure comprising of a uniform Dy-lean core–Dy-rich shell in a series of multi-main-phase (MMP) Nd–Dy–Fe–B magnets. The resulting MMP Dy1 and Dy3 magnets with an overall Dy level of 1 and 3 wt.% possessed values of 0.48 and 0.29 T/wt.% of coercivity increment per unit weight percentage of the Dy addition, respectively. Most importantly, the resulting MMP Dy3 magnet exhibited a high coercivity (2.38 T), an excellent thermal stability of the coercivity (|β| = 0.531%/°C), a high squareness factor (> 95%), all with little diminishment in the remanent magnetisation (1.35 T) and maximum energy product (43.6 MGOe). These properties are superior to the currently available sintered Nd–Dy–Fe–B magnets which utilise higher levels of Dy of 5 wt.%. Via magnetic and multi-scale microstructural characterisation experiments and micromagnetic simulations, the formation of the Dy-lean core–Dy-rich shell microstructure is rationalised via solid-state-diffusion and solution reprecipitation during liquid-phase sintering. The Dy-lean core–Dy-rich shell microstructure and the non-ferromagnetic low-Fe RE-rich grain boundary phase led to the synergistic magnetic performance. This is significant in the context of the MMP Nd–Dy–Fe–B magnets being applied to large-scale production. The present work establishes a pathway for the more sustainable utilisation of Dy in permanent magnets via formation of a uniform core–shell microstructure.
| Original language | English |
|---|---|
| Article number | 119344 |
| Journal | Acta Materialia |
| Volume | 261 |
| DOIs | |
| State | Published - Dec 1 2023 |
Funding
This work was supported by National Key Research and Development Program of China (2021YFB3501504), National Natural Science Foundation of China (U21A2052), Key Research and Development Program of Zhejiang Province (2021C01192), “Leading Goose” R&D Program of Zhejiang Province (2022C01110), and 2022 USYD-ZJU Parternership Collaboration Awards (PCA). The authors thank Dr. Xiangyuang Cui, Dr. Vijay Bhatia, Dr. Takanori Sato and Mr. Jacob Byrnes at the University of Sydney, Prof. Zijian Hong, Associate Prof. Yuhui Huang, Prof. Yongjun Wu at Zhejiang University, and Prof. Tianyu Ma at the Xi'an Jiaotong University for their technical support and discussions. SPR acknowledges partial financial support from the Australian Research Council Discovery Program (DP200100940). The authors acknowledge the facilities, and the scientific and technical assistance of Sydney Microscopy & Microanalysis, which is the University of Sydney's node of Microscopy Australia node. This work was supported by National Key Research and Development Program of China ( 2021YFB3501504 ), National Natural Science Foundation of China ( U21A2052 ), Key Research and Development Program of Zhejiang Province ( 2021C01192 ), “Leading Goose” R&D Program of Zhejiang Province ( 2022C01110 ), and 2022 USYD-ZJU Parternership Collaboration Awards (PCA). The authors thank Dr. Xiangyuang Cui, Dr. Vijay Bhatia, Dr. Takanori Sato and Mr. Jacob Byrnes at the University of Sydney, Prof. Zijian Hong, Associate Prof. Yuhui Huang, Prof. Yongjun Wu at Zhejiang University, and Prof. Tianyu Ma at the Xi'an Jiaotong University for their technical support and discussions. SPR acknowledges partial financial support from the Australian Research Council Discovery Program ( DP200100940 ). The authors acknowledge the facilities, and the scientific and technical assistance of Sydney Microscopy & Microanalysis, which is the University of Sydney's node of Microscopy Australia node.
Keywords
- Coercivity
- Core–shell microstructure
- Liquid-phase sintering
- Multi-main-phase Nd–Dy–Fe–B
- Permanent magnets