Macroscopically heterogeneous grain boundary diffusion process for efficient coercivity enhancement of Nd-Fe-B magnets

Article Chemistry, Multidisciplinary

Understanding the Role of Element Grain Boundary Diffusion Mechanism in Nd-Fe-B Magnets

Lizhong Zhao et al.

Summary: The study investigates the synergistic effects of three rare earth elements in permanent magnets, achieving high performance and revealing the role of element GBD mechanism.

ADVANCED FUNCTIONAL MATERIALS (2022)

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Article Physics, Applied

High-efficient selected area grain boundary diffusion for enhancing the coercivity of thick Nd-Fe-B magnets

Jiayi He et al.

Summary: A novel approach known as selected area GBD (SAGBD) is proposed for treating thick Nd-Fe-B magnets, aiming to enhance coercivity by diffusing the source mainly from the edges and corners. Microstructure characterizations and micromagnetic simulation revealed that the edges and corners are weak magnetic areas of the magnet, and SAGBD can effectively hinder the formation of reversed domains in these areas and the rapid reversal propagation throughout the magnet.

APPLIED PHYSICS LETTERS (2022)

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Review Materials Science, Multidisciplinary

Development of non-rare earth grain boundary modification techniques for Nd-Fe-B permanent magnets

Zhongwu Liu et al.

Summary: The magnetic performance of Nd-Fe-B magnets is dependent on the grain boundary structure. Intergranular addition and grain boundary diffusion (GBD) processes using non-rare earth sources have been effective in enhancing coercivity. This review summarizes the development and use of non-RE diffusion sources for coercivity enhancement, discussing the properties-microstructure relationships and future directions for non-RE GBD.

JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY (2022)

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Article Chemistry, Physical

Pr80Al20 surface-coated DyF3 modified sintered Nd-Fe-B magnets for large coercivity increment via grain boundary diffusion

Feifei Li et al.

Summary: By utilizing composite powders for grain boundary diffusion, a significant improvement in coercivity of magnets can be achieved, while optimizing the microstructure can enhance the temperature coefficient of coercivity. Improved Pr-Al-rich grain boundary phases contribute to excellent diffusion efficiency and Dy diffusion depth.

JOURNAL OF ALLOYS AND COMPOUNDS (2022)

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Article Materials Science, Multidisciplinary

Enhancing the grain boundary diffusion efficiency of Tb for Nd-Fe-B magnets using dual-alloy diffusion source

Wenyue Song et al.

Summary: Grain boundary diffusion is an effective method to enhance coercivity for Nd-Fe-B magnets with reduced consumption of heavy rare earths. This study proposes a dual-alloy diffusion source to improve the diffusion of Tb element, which significantly enhances the coercivity and magnetic hysteresis loop squareness of the magnet. The use of a dual-alloy diffusion source allows for efficient utilization of HRE resources and increased infiltration depth, making it attractive for industrial applications.

JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T (2022)

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Article Materials Science, Multidisciplinary

Review of additive manufacturing of permanent magnets for electrical machines: A prospective on wind turbine

H. Wang et al.

Summary: Permanent magnets (PMs) are crucial in powering various industrial technologies that contribute to our modern society and high standards of living. This paper discusses the roles, challenges, and advantages of utilizing PMs, and explores the potential of additive manufacturing (AM) for PM manufacturing. The future outlook of using AM processes for PM production is also provided.

MATERIALS TODAY PHYSICS (2022)

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Article Chemistry, Physical

Reducing the process consumption of Tb in grain boundary diffusion of Nd-Fe-B magnets by sputtering deposition instead of adhesive coating

Jiayi He et al.

Summary: A comparative study on coating methods of adhesive coating and sputtering deposition was conducted to evaluate their effects on the surface state of diffused magnet and the process consumption of heavy rare earths (HREs). The results show that sputtering deposition can significantly enhance the coercivity of the magnet and reduce the consumption of Tb.

JOURNAL OF ALLOYS AND COMPOUNDS (2022)

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Article Materials Science, Multidisciplinary

On the anisotropic grain boundary diffusion of sintered Nd-Fe-B magnets

Wenyue Song et al.

Summary: Under certain conditions, the diffusion efficiency of heavy rare earth elements along the a-axis can be comparable to that along the c-axis. Alloying can enhance the diffusion along the a-axis, resulting in increased coercivity and reduced total consumption.

MATERIALS LETTERS (2022)

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Article Chemistry, Physical

Alloying Pr-Tb-Cu diffusion source with Ni for enhancing both coercivity and corrosion resistance of Nd-Fe-B magnets

Jiali Cao et al.

Summary: Grain boundary diffusion of heavy rare earth-based alloys can effectively enhance the coercivity and corrosion resistance of Nd-Fe-B magnets. The use of Ni alloy diffusion source improves the diffusion process and increases the coercivity and chemical stability of the magnets.

JOURNAL OF ALLOYS AND COMPOUNDS (2022)

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Article Materials Science, Multidisciplinary

Microstructure optimization and coercivity enhancement of Nd-Fe-B magnet by double-step diffusion with Pr60Cu20Al20 alloy and Tb metal

Haijun Yu et al.

Summary: Sintered Nd-Fe-B magnets were processed using single-step diffusion (SSD) and double-step diffusion (DSD) techniques with Tb metal and Pr60Cu20Al20 alloy. The coercivity of the magnets increased with both SSD and DSD, with DSD showing the highest coercivity. The microstructure analysis revealed that the formation of (Nd, Tb)2Fe14B phases enhanced the coercivity. The presence of Tb-poor anti-shells was found near the surface of the diffused magnets, but pre-diffusion of Pr60Cu20Al20 alloy improved the distribution of grain boundary phases in the DSD magnets, resulting in thinner anti-core/shell region layers compared to SSD magnets.

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS (2022)

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Article Chemistry, Physical

Microstructural insights into the coercivity enhancement of grain-boundary-diffusion-processed Tb-treated Nd-Fe-B sintered magnets beyond the core-shell formation mechanism

Kristina Zagar Soderznik et al.

Summary: This study proposed a dominant core-shell formation mechanism for Nd2Fe14B sintered magnets processed with grain-boundary diffusion and Tb treatment, demonstrating a 30% increase in coercivity with GBDP mechanism. The results revealed that Tb diffuses along grain boundaries to form a core-shell structure, leading to enhanced magnetic properties. The measured increase in coercivity was attributed to a structural effect caused by the presence of Tb rather than its magnetic contribution, paving the way for grain-boundary engineering studies to enhance the coercivity of Nd-Fe-B magnets for e-mobility and eco-power applications.

JOURNAL OF ALLOYS AND COMPOUNDS (2021)

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Article Materials Science, Multidisciplinary

High coercivity Nd-Fe-B magnet with low Tb concentration by combined diffusion

Shuai Cao et al.

Summary: The commercial N50 Nd-Fe-B magnet underwent a combined diffusion process with Pr65Cu15Al20 and Pr50Tb30Al20, resulting in an increase in coercivity and the formation of uniform Tb-rich shells. The combined diffusion process proved effective in promoting Tb diffusion along grain boundaries and enhancing Tb availability.

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS (2021)

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Article Chemistry, Physical

Annealed Al-Cr coating: A hard anti-corrosion coating with grain boundary modification effect for Nd-Fe-B magnets

Jiayi He et al.

Summary: A novel method of using annealed Al-Cr coating is proposed to achieve surface protection, grain boundary modification, and enhanced performance of Nd-Fe-B magnets. The addition of Cr significantly improves the hardness of Al coating and modifies the diffusion process of Al. The coated magnets exhibit high hardness, strong adhesion, sufficient corrosion resistance, good anti-oxidation, and improved coercivity.

JOURNAL OF ALLOYS AND COMPOUNDS (2021)

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Article Materials Science, Multidisciplinary

Grain boundary oxide layers in NdFeB-based permanent magnets

A. Mazilkin et al.

Summary: The microstructure of grain boundaries in commercial NdFeB-based alloy for permanent magnets reveals the presence of neodymium oxide Nd2O3 layers which contribute to magnetic isolation between Nd2Fe14B grains, enhancing coercivity of the alloy.

MATERIALS & DESIGN (2021)

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Review Materials Science, Multidisciplinary

Significant progress of grain boundary diffusion process for cost-effective rare earth permanent magnets: A review

Zhongwu Liu et al.

Summary: This review provides a critical description of the fundamentals and development of grain boundary diffusion process (GBDP) for enhancing coercivity of Nd-Fe-B magnets. It discusses the mechanisms, cost reduction, and challenges and opportunities for future development of GBDP and cost-effective permanent magnets.

MATERIALS & DESIGN (2021)

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Article Chemistry, Physical

A novel strategy to design and fabricate Nd-Fe-B magnets

Fugang Chen et al.

Summary: The demagnetization field distribution of magnetized Nd-Fe-B magnet was quantitatively calculated and analyzed. Multilayered composite Nd-Fe-B magnets were designed and fabricated with specific coercivity gradient distributions lower than the demagnetization field gradient. It was found that the low coercivity interlayer magnets did not significantly decrease the overall magnetic properties, and effective self-bonding was observed between adjacent Nd-Fe-B magnets.

JOURNAL OF ALLOYS AND COMPOUNDS (2021)

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Review Materials Science, Multidisciplinary

Grain Boundary Diffusion Sources and Their Coating Methods for Nd-Fe-B Permanent Magnets

Jiayi He et al.

Summary: Grain boundary diffusion (GBD) is the best route for fabricating high-coercive Nd-Fe-B magnets, with the development of new diffusion sources expanding the application of GBD to include non-rare earth elements. The advancement of various coating methods improves the adhesion of diffusion sources, optimizing the fabrication process further.

METALS (2021)

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Article Materials Science, Multidisciplinary

Towards the diffusion source cost reduction for NdFeB grain boundary diffusion process

H. X. Zeng et al.

JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY (2020)

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Article Materials Science, Multidisciplinary

Microstructure evolution and coercivity enhancment of sintered Nd?Fe?B magnets by grain boundary diffusion with Cu aided TbF3

Xi Gao et al.

MATERIALS RESEARCH EXPRESS (2020)

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Article Nanoscience & Nanotechnology

Formation mechanism of Tb-rich shell in grain boundary diffusion processed Nd-Fe-B sintered magnets

Tae-Hoon Kim et al.

SCRIPTA MATERIALIA (2020)

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Article Materials Science, Multidisciplinary

Significantly enhancing the coercivity of NdFeB magnets by ternary Pr-Al-Cu alloys diffusion and understanding the elements diffusion behavior

Huixin Zeng et al.

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS (2019)

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Article Materials Science, Multidisciplinary

Coercivity enhancement of Nd-Fe-B sintered magnet by grain boundary diffusion process using Pr-Tb-Cu-Al alloys

Kechao Lu et al.

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS (2019)

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Article Materials Science, Multidisciplinary

Micromagnetic simulation of anisotropic grain boundary diffusion for sintered Nd-Fe-B magnets

W. Li et al.

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS (2018)

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Article Nanoscience & Nanotechnology

Highly efficient Tb-utilization in sintered Nd-Fe-B magnets by Al aided TbH2 grain boundary diffusion

Jinghui Di et al.

SCRIPTA MATERIALIA (2018)

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Article Materials Science, Multidisciplinary

Influence of annealing on microstructural and magnetic properties of Nd-Fe-B magnets by grain boundary diffusion with Pr-Cu and Dy-Cu alloys

Kechao Lu et al.

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS (2017)

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Article Nanoscience & Nanotechnology

Micromagnetic simulation of the influence of grain boundary on cerium substituted Nd-Fe-B magnets

D. Liu et al.

AIP ADVANCES (2017)

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Article Materials Science, Multidisciplinary

Experimental and computational analysis of magnetization reversal in (Nd,Dy)-Fe-B core shell sintered magnets

Tim Helbig et al.

ACTA MATERIALIA (2017)

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Article Materials Science, Multidisciplinary

Grain boundary diffusion of different rare earth elements in Nd-Fe-B sintered magnets by experiment and FEM simulation

K. Loewe et al.

ACTA MATERIALIA (2017)

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Article Materials Science, Multidisciplinary

Anisotropic diffusion mechanism in grain boundary diffusion processed Nd-Fe-B sintered magnet

Tae-Hoon Kim et al.

ACTA MATERIALIA (2016)

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Article Nanoscience & Nanotechnology

Large-scale micromagnetic simulation of Nd-Fe-B sintered magnets with Dy-rich shell structures

T. Oikawa et al.

AIP ADVANCES (2016)

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Article Materials Science, Multidisciplinary

Simultaneous application of Dy-X (X = F or H) powder doping and dip-coating processes to Nd-Fe-B sintered magnets

Tae-Hoon Kim et al.

ACTA MATERIALIA (2015)

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Article Materials Science, Multidisciplinary

Temperature-dependent Dy diffusion processes in Nd-Fe-B permanent magnets

K. Loeewe et al.

ACTA MATERIALIA (2015)

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Article Nanoscience & Nanotechnology

Coercivity enhancement of a Nd-Fe-B sintered magnet by diffusion of Nd70Cu30 alloy under pressure

Fugang Chen et al.

SCRIPTA MATERIALIA (2015)

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Article Chemistry, Physical

Faceted shell structure in grain boundary diffusion-processed sintered Nd-Fe-B magnets

U. M. R. Seelam et al.

JOURNAL OF ALLOYS AND COMPOUNDS (2014)

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Article Nanoscience & Nanotechnology

Micromagnetic simulations on the grain size dependence of coercivity in anisotropic Nd-Fe-B sintered magnets

H. Sepehri-Amin et al.

SCRIPTA MATERIALIA (2014)

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Article Nanoscience & Nanotechnology

Enhancement of coercivity of hot-deformed Nd-Fe-B anisotropic magnet by low-temperature grain boundary diffusion of Nd60Dy20Cu20 eutectic alloy

H. Sepehri-Amin et al.

SCRIPTA MATERIALIA (2013)

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Article Chemistry, Physical

A study on the Nd-rich phase evolution in the Nd-Fe-B sintered magnet and its mechanism during post-sintering annealing

Tae-Hoon Kim et al.

JOURNAL OF ALLOYS AND COMPOUNDS (2012)

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Article Materials Science, Multidisciplinary

Production of thick high-performance sintered neodymium magnets by grain boundary diffusion treatment with dysprosium-nickel-aluminum alloy

Naoko Oono et al.

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS (2011)

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Article Physics, Applied

Current status and recent topics of rare-earth permanent magnets

S. Sugimoto

JOURNAL OF PHYSICS D-APPLIED PHYSICS (2011)

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Article Nanoscience & Nanotechnology

Coercivity enhancement of hydrogenation-disproportionation-desorption-recombination processed Nd-Fe-B powders by the diffusion of Nd-Cu eutectic alloys

H. Sepehri-Amin et al.

SCRIPTA MATERIALIA (2010)

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Article Materials Science, Multidisciplinary

Effect of post-sinter annealing on the coercivity and microstructure of Nd-Fe-B permanent magnets

W. F. Li et al.

ACTA MATERIALIA (2009)

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Macroscopically heterogeneous grain boundary diffusion process for efficient coercivity enhancement of Nd-Fe-B magnets

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