Grain Boundary Structure and Coercivity Enhancement of Nd90Al10 Alloy Modified NdFeB Permanent Magnets by GBD Process

doi:10.11900/0412.1961.2021.00471

Acta Metall Sin

2023, Vol. 59

Issue (11): 1457-1465 DOI: 10.11900/0412.1961.2021.00471

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Grain Boundary Structure and Coercivity Enhancement of Nd₉₀Al₁₀ Alloy Modified NdFeB Permanent Magnets by GBD Process

LIU Lujun¹, LIU Zheng²(

), LIU Renhui³, LIU Yong¹

^1.Faculty of Materials Metallurgy and Chemistry, Jiangxi University of Science and Technology, Ganzhou 341000, China
^2.School of Mechanical and Electronical Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, China
^3.Jiangxi Key Laboratory for Rare Earth Magnetic Material and Devices, Jiangxi University of Science and Technology, Ganzhou 341000, China

Cite this article:

LIU Lujun, LIU Zheng, LIU Renhui, LIU Yong. Grain Boundary Structure and Coercivity Enhancement of Nd₉₀Al₁₀ Alloy Modified NdFeB Permanent Magnets by GBD Process. Acta Metall Sin, 2023, 59(11): 1457-1465.

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Abstract

The grain boundary diffusion (GBD) process is a remarkable achievement in sintered Nd-Fe-B permanent magnet manufacturing. Furthermore, the coercivity can be considerably improved by diffusing heavy rare earth (HRE) elements into the magnet along the grain boundary, and the reduced HRE consumption can also be realized. However, compared with parameters of GBD, previous research has focused less on improving the magnet. In this study, the magnet was prepared using low melting point alloy Nd₉₀Al₁₀ before GBD modification, after which the corresponding Tb-GBD was completed. The magnetic property results indicated that the coercivity increased to 1439 kA/m, which was 530 kA/m higher than the unmodified magnet. Thus, the effects of the grain boundary structure and composition on the coercivity were analyzed. The addition of Nd₉₀Al₁₀ did not affect the Curie temperature of the magnet, but it reduced the low-temperature phase transition temperature. The Tb replaced Nd at the margin of main phase, which moved the diffraction peak to the right in the XRD spectrum. Moreover, a clear Tb-rich shell surrounding the main phase formed in the diffused magnet modified by Nd₉₀Al₁₀ at the depth of 20 μm, and the shell could still be clearly observed at 100 μm. However, the main phase was surrounded by the continuous grain boundary when the depth increased to 500 μm in Nd₉₀Al₁₀ modified magnet by GBD. The Tb-rich shell was observed by TEM and a noncrystalline Nd-rich phase was observed. The content peak of the Nd element appeared in the central region of the Nd-rich phase. This, the diffused depth and usage efficiency remarkably improved, because the Nd-rich phase acted as a channel for Tb diffusion, with the concentration of Tb being as high as 35%.

Key words: sintered Nd-Fe-B magnet grain boundary diffusion coercivity grain boundary modification

Received: 01 November 2021

ZTFLH:

TM273

Fund: High Technology Research and Development Program of China(2010AA03A0401)

Corresponding Authors: LIU Zheng, professor, Tel: 13879729585, E-mail: liukk66@163.com

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https://www.ams.org.cn/EN/10.11900/0412.1961.2021.00471 OR https://www.ams.org.cn/EN/Y2023/V59/I11/1457

Fig.1 DSC curves of original (A0) and the 0.5%Nd₉₀Al₁₀modified (A1) magnets

Fig.2 XRD spectra of A0 and AMG magnets (a) and details in the regin of 59°-62° (b) (AMG—0.5%Nd₉₀Al₁₀ modification with grain boundary diffusion (GBD) treatment)

Fig.3 Magnetic properties at room temperature of A0, AG, and AMG magnets (AG—unmodified GBD; B_r—residual magnetism, H_cj—coercivity)

Fig.4 BSE images of microstructures of AG (a1-a4) and AMG (b1-b4) magnets with different depths from surface (1: Nd₂Fe₁₄B, 2: Nb-rich phse, 3: Tb-rich shell)
(a1, b1) 20 μm (a2, b2) 100 μm (a3, b3) 500 μm (a4, b4) 900 μm

Fig.5 High-angle annular dark field (HAADF) image (a) and SAED patterns of area A (b) and area B (c) of AMG magnet (1: Nd₂Fe₁₄B, 2: Tb-rich shell, 3: Nd-rich phase) (Inset in Fig.5b shows the interplanar spacing)

Fig.6 SEM images (a, b) and element distributions in Nd-rich phase of Fe (a1, b1), Pr (a2, b2), Nd (a3, b3), and Tb (a4, b4) of AG (a-a4) and AMG (b-b4) magnets

1	Bai G, Gao R. W, Sun Y, et al. Study of high-coercivity sintered NdFeB magnets [J]. J. Magn. Magn. Mater., 2007, 308: 20 doi: 10.1016/j.jmmm.2006.04.029
2	Yan G H, Chen R J, Ding Y, et al. The preparation of sintered NdFeB magnet with high-coercivity and high temperature-stability [J]. J. Phys. Conf. Ser., 2011, 266: 012052
3	Hirosawa S, Matsuura Y, Yamamoto H, et al. Magnetization and magnetic anisotropy of R₂Fe₁₄B measured on single crystals [J]. J. Appl. Phys., 1986, 59: 873 doi: 10.1063/1.336611
4	Oono N, Sagawa M, Kasada R, et al. Production of thick high-performance sintered neodymium magnets by grain boundary diffusion treatment with dysprosium-nickel-aluminum alloy [J]. J. Magn. Magn. Mater., 2011, 323: 297 doi: 10.1016/j.jmmm.2010.09.021
5	Wang J, Liang L, Wu M Y, et al. Research progress on grain boundary fine microstructure and magnetic properties of sintered NdFeB magnet [J]. Chin. J. Nonferrous Met., 2014, 24: 1562 doi: 10.1016/S1003-6326(14)63226-X
	王静, 梁乐, 武梦艳等. 烧结NdFeB永磁体的晶界微细结构及性能研究进展 [J]. 中国有色金属学报, 2014, 24: 1562
6	Wang X L, Zhao L N, Ding K H, et al. Influence of dysprosium distribution on properties of sintered and aged Dy-doped NdFeB permanent magnets [J]. Rare Met. Mater. Eng., 2016, 45: 309 doi: 10.1016/S1875-5372(16)30060-1
7	Chen B C, Liu X M, Chen R J, et al. Design and fabrication of Dy-free sintered permanent magnets with high coercivity [J]. J. Appl. Phys., 2012, 111: 07A710
8	Dormidontov N A, Dormidontov A G, Lileev A S, et al. Effect of partial substitution of neodymium with praseodymium on the magnetic and process properties of sintered magnets of type NdFeB [J]. Met. Sci. Heat Treat., 2017, 58: 608 doi: 10.1007/s11041-017-0064-6
9	Park K T, Hiraga K, Sagawa M. Effect of metal-coating and consecutive heat treatment on coercivity of thin Nd-Fe-B sintered magnets [A]. Proceeding of the 16th International Workshop on Rare-Earth Magnets and Their Applications [C]. Sendai, Japan: Japan Institute of Metals, 2000: 257
10	Nakamura H, Hirota K, Shimao M, et al. Magnetic properties of extremely small Nd-Fe-B sintered magnets [J]. IEEE Trans. Magnet., 2005, 41: 3844 doi: 10.1109/TMAG.2005.854874
11	Cui X G, Wang X H, Cui C Y, et al. Research progress in Grain boundary diffusion modification, microstructures and properties of sintered Nd-Fe-B magnets [J]. Chin. J. Rare Met., 2018, 42: 315
	崔熙贵, 王兴华, 崔承云等. 烧结钕铁硼的晶界扩散改性、结构与性能研究进展 [J]. 稀有金属, 2018, 42: 315
12	Tan M, Zhao Y, Chen H S, et al. Research progress on grain boundary diffused Nd-Fe-B magnets [J]. Powder Metall. Ind., 2019, 29(2): 66
	谭敏, 赵扬, 陈红升等. 钕铁硼晶界扩散研究进展 [J]. 粉末冶金工业, 2019, 29(2): 66
13	Suzuki H, Satsu Y, Komuro M. Magnetic properties of a Nd-Fe-B sintered magnet with Dy segregation [J]. J. Appl. Phys., 2009, 105: 07A734
14	Li D S, Suzuki S, Kawasaki T, et al. Grain interface modification and magnetic properties of Nd-Fe-B sintered magnets [J]. Jpn. J. Appl. Phys., 2008, 47: 7876 doi: 10.1143/JJAP.47.7876
15	Popov A G, Vasilenko D Y, Puzanova T Z, et al. Effect of diffusion annealing on the hysteretic properties of sintered Nd-Fe-B magnets [J]. Phys. Met. Metall., 2011, 111: 471 doi: 10.1134/S0031918X11040107
16	Sun X X, Bao X Q, Gao X X, et al. Effect of dysprosium addition by pack cementation on magnetic properties and microstructure of Nd-Fe-B sintered magnets [J]. Chin. J. Rare Met., 2009, 27: 86
	孙绪新, 包小倩, 高学绪等. 烧结Nd-Fe-B磁体表面渗镀Dy₂O₃对磁体显微组织和磁性能的影响 [J]. 中国稀土学报, 2009, 27: 86
17	Zhang L G, Liu L B, Jin Z P. The Phase Diagrams and Application of Al-Cu-Re System [M]. Changsha: Central South University Press, 2015: 1
	章立钢, 刘立斌, 金展鹏. 稀土A1-Cu合金相图及应用 [M]. 长沙: 中南大学出版社, 2015: 1
18	Di J H. Study on the effect of Al and rare earth grain boundary Co-diffusion on the microstructure and coercivity of sintered Nd-Fe-B magnets [D]. Ningbo: Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, 2019
	邸敬慧. Al和稀土元素共晶界扩散对烧结Nd-Fe-B磁体微观结构和矫顽力影响的研究 [D]. 宁波: 中国科学院大学(中国科学院宁波材料技术与工程研究所), 2019
19	Kim T H, Lee S R, Namkumg S, et al. A study on the Nd-rich phase evolution in the Nd-Fe-B sintered magnet and its mechanism during post-sintering annealing [J]. J. Alloys Compd., 2012, 537: 261 doi: 10.1016/j.jallcom.2012.05.075
20	Knoch K G, Grieb B, Henig E T, et al. Upgraded Nd-Fe-B-AD (AD = Al,Ga) magnets: Wettability and microstructure [J]. IEEE Trans. Magnet., 1990, 26: 1951 doi: 10.1109/20.104918
21	Goto R, Nishio S, Matsuura M, et al. Wettability and interfacial microstructure between Nd₂Fe₁₄B and Nd-rich phases in Nd-Fe-B alloys [J]. IEEE Trans. Magnet., 2008, 44: 4232 doi: 10.1109/TMAG.2008.2001544
22	Nishio S, Sugimoto S, Goto R, et al. Effect of Cu addition on the phase equilibria in Nd-Fe-B sintered magnets [J]. Mater. Trans., 2009, 50: 723 doi: 10.2320/matertrans.MBW200824
23	Kim T H, Lee S R, Bae K H, et al. Effects of Al/Cu co-doping on crystal structure and chemical composition of Nd-rich phases in Nd-Fe-B sintered magnet [J]. Acta Mater., 2017, 133: 200 doi: 10.1016/j.actamat.2017.05.046
24	Chen F G, Jin Y X, Cheng Y, et al. Investigation of the wettability and the interface feature of the melted Nd₇₀Cu₃₀ alloy on the surface of a sintered Nd-Fe-B magnet [J]. Scr. Mater., 2018, 157: 135 doi: 10.1016/j.scriptamat.2018.08.014
25	Kim T H, Lee S R, Yun S J, et al. Anisotropic diffusion mechanism in grain boundary diffusion processed Nd-Fe-B sintered magnet [J]. Acta Mater., 2016, 112: 59 doi: 10.1016/j.actamat.2016.04.019
26	You C Y, Lu Z X, Qiao Y, et al. Microstructure characterization and its relationship with magnetic properties of sintered Nd-Fe-B magnet [A]. Proceedings of the 7th Chinese Academic Conference on Functional Materials and Their Applications [C]. Changsha: China Instrumentation Society, China Metal Society, 2010: 314
	游才印, 卢正欣, 乔玉等. 烧结钕铁硼磁体的微结构表征及其与磁性能的关系研究 [A]. 第七届中国功能材料及其应用学术会议论文集 [C]. 长沙: 中国仪器仪表学会, 中国金属学会, 2010: 314
27	Xu F. Effects of grain boundary structure and chemistry on the coercivity of NdFeB materials [D]. Shanghai: Shanghai Jiao Tong University, 2011
	徐芳. 晶界结构和晶界化学对NdFeB材料矫顽力的影响 [D]. 上海: 上海交通大学, 2011
28	Oikawa T, Yokota H, Ohkubo T, et al. Large-scale micromagnetic simulation of Nd-Fe-B sintered magnets with Dy-rich shell structures [J]. AIP Adv., 2016, 6: 056006
29	Périgo E A, Titov I, Weber R, et al. Small-angle neutron scattering study of coercivity enhancement in grain-boundary-diffused Nd-Fe-B sintered magnets [J]. J. Alloys Compd., 2016, 677: 139 doi: 10.1016/j.jallcom.2016.03.160

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[2]	LIU Zhongwu, HE Jiayi. Several Issues on the Development of Grain Boundary Diffusion Process for Nd-Fe-B Permanent Magnets[J]. 金属学报, 2021, 57(9): 1155-1170.
[3]	Shaoting GONG, Chengbao JIANG, Tianli ZHANG. Effect of Fe on Microstructure and Coercivity of SmCo-Based Magnets[J]. 金属学报, 2017, 53(6): 726-732.
[4]	WANG Qian JIANG Chengbao. STUDY ON SmCo PERMANENT MAGNETS UNDER 350℃ MODERATE TEMPERATURES[J]. 金属学报, 2011, 47(12): 1605-1610.
[5]	BAO Xiaoqian GAO Xuexu ZHU Jie ZHANG Maocai ZHOU Shouzeng. EFFECTS OF Nd CONTENT ON MAGNETIC PROPERTIES OF NANOCRYSTALLINE Nd_xFe_94-xB₆ ALLOYS[J]. 金属学报, 2009, 45(8): 988-993.
[6]	Gao Xue-xu. Preparation of high coercivity and high thermal stability sintered Nd-Fe-B magnet by optimizing boundary microstructure[J]. 金属学报, 2008, 44(7): 871-875 .
[7]	XIAO Yaofu; ZHANG Zhengyi; TANG Weizhong (University of Science and Technology Beijing). AN APPROACH TO PREPARING NdFeB POWDER WITH HIGH COERCIVITY[J]. 金属学报, 1992, 28(8): 91-94.
[8]	ZHANG Yanzhong;NIAN Suzhen Shanghai Iron and Steel Research Institure Correspondent; senior; engineer; Shanghai Iron and Steel research Institute; Shanghai 200940. THREE NEW Fe-BASED MICROCRYSTALLINE ALLOYS WITH SUPERIOR MAGNETIC PROPERTIES[J]. 金属学报, 1992, 28(6): 76-84.
[9]	ZHOU Shouzeng;ZHANG Jin;MA Deqing;GAO Maolin University of Science and Technology Beijing. MICROSTRUCTURE AND MAGNETIC HARDENING OF SINTERED NdFeB MAGNETS DOPING Dy OR Dy_2O_3[J]. 金属学报, 1992, 28(3): 69-74.
[10]	CHEN Zhongmin;XIE Faqin;SHI Zhengxing;WANG Leyi;FU Hengzhi Northwestern Polytechnical University; Xi'an. COERCIVITY AND ITS GRAIN SIZE DEPENDENCE IN CAST-HOT PRESSED Pr-Fe-B MAGNETS[J]. 金属学报, 1991, 27(5): 125-129.
[11]	ZHOU Shouzeng;TANG Weizhong;WANG Run University of Science and Technology Beijing associate professor;Department of Materials Science;University of Science and Technology Beijing; Beijing 100083. BOUNDARY MICROSTRUCTURE AND MAGNETIC HARDENING OF SINTERED NdFeB MAGNET[J]. 金属学报, 1990, 26(4): 148-152.
[12]	YANG Guobin;GUAN Zhiqun;WANG Shuangquan;WANG Run Beijing University of Iron and Steel TechnologyProfessor;Department of Materials Science; Beijing University of Iron and Steel Technology. INFLECTION OF COERCIVITY DURING LOCAL CRYSTALLIZATION OF Fe-Si-B AMORPHOUS ALLOYS[J]. 金属学报, 1988, 24(4): 362-364.

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