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With the aim of increasing Cu concentration to regulate the distribution of Co elements in RE-rich phase, the low-melting-point Pr80Cu20 intergranular alloy is introduced into the (Pr, Nd, Dy)32.2Co13Cu0.4FebalB0.98M1.05 (M = Al, Ga, Zr) magnet. Comparing with the original magnet, the remanence of PrCu-doped magnet is basically unchanged, and the coercivity is increased by approximately 1.3 kOe. Simultaneously, the Curie temperature, remanence temperature coefficient and irreversible flux loss are slightly improved. Microstructural study reveals that the Co-lean phase and the Co-rich phase coexist in the grain boundary in the 2nd-annealed original magnet. However, for the PrCu-doped magnet, the uniform distribution of Cu and Co elements in the intergranular phase are evidently improved, resulting in the elimination of the Co-rich phase. Since the R2(Fe, Co)17 (R = Pr, Nd, Dy) soft magnetic phase easily coexist with the Co-rich phase and are detrimental to the coercivity, the elimination of Co-rich intergranular phase may be an important reason for the higher coercivity of the 2nd-annealed PrCu-doped magnet than that of the original magnet.
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Keywords:
- sintered NdFeB magnet /
- intergranular addition /
- annealing /
- opposite distribution between Cu and Co /
- coercivity
[1] Sagawa M, Fujimura S, Togawa N, Yamamoto H, Matsuura Y 1984 J. Appl. Phys. 55 2083
Google Scholar
[2] Yan G L, McGuiness P J, Farr J P G, Harris I R 2010 J. Alloys Compd. J. Alloys Compd. 491 L20
Google Scholar
[3] Mottram R S, Williams A J, Harris I R 2000 J. Magn. Magn. Mater. 217 27
Google Scholar
[4] Hu Z H, Lian F Z, Zhu M G, Li W 2008 J. Magn. Magn. Mater. 320 2364
Google Scholar
[5] Kostyuchenko N V, Tereshina I S, Gorbunoy D I, Tereshina-Chitrova E A, Rogacki K, Andreev A V, Doerr M, Politova G A, Zvezdin A K 2020 Intermetallics 124 106840
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Li D, Dong S Z, Li L, Xu J Y, Chen H S, Li W 2020 Acta Phys. Sin. 69 147501
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Google Scholar
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[16] 张家滕, 徐吉元, 胡成林, 孟睿阳, 董生智 2022 中国稀土学报 40 235
Zhang J T, Xu J Y, Hu C L, Meng R Y, Dong S Z. 2022 J. Chin. Rare Earth Soc. 40 235
[17] 胡伯平, 饶晓雷, 王亦忠 2017 稀土永磁材料(上册) (北京: 冶金工业出版社) 第197页
Hu B P, Rao X L, Wang Y Z 2017 Rare-earth Permanent Magnet Materials (Vol. 1) (Beijing: Metallurgical Industry Press) p197 (in Chinese)
[18] Kou X C, Zhao T S, R. Grössinger, de Boer F R 1992 Phys. Rev. B 46 6225
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图 1 原磁体和掺PrCu磁体二级回火态样品不同温度下的退磁曲线
Figure 1. Demagnetization curves of the 2nd-annealed original-magnet and PrCu-doped magnet upon elevated temperatures.
图 2 原磁体和掺PrCu磁体的温度稳定性对比 (a), (d) TG/DTG曲线; (b), (e) 不可逆磁损曲线; (c), (f) 剩磁温度系数
Figure 2. Comparison of temperature stability of magnetic properties between original-magnet and PrCu-doped magnet: (a), (d) TG/DTG curves; (b), (e) irreversible flux loss curves; (c), (f) remanence temperature coefficient.
图 3 (a) 原磁体烧结态、(b) 一级回火态和(c)二级回火态样品的扫描电镜背散射照片(BSE)及对应区域的能谱照片(EDS)
Figure 3. SEM figure (BSE) and EDS figure of the corresponding region of original-magnet (a) as-sintered, (b) 1st-annealing and (c) 2nd-annealing.
图 4 (a) 掺PrCu磁体烧结态、(b) 一级回火态和(c)二级回火态样品的扫描电镜背散射照片(BSE)及对应区域的能谱照片(EDS)
Figure 4. SEM figure (BSE) and EDS figure of the corresponding region of PrCu-doped magnet (a) as-sintered, (b) 1st-annealing and (c) 2nd-annealing.
图 5 原磁体透射电镜明场像照片(BF)及对应区域的元素面分布 (a) 烧结态; (b) 一级回火态; (c) 二级回火态
Figure 5. Bright field image (BF) and corresponding EDX mapping of original-magnet: (a) As-sintered; (b) 1st-annealing; (c) 2nd-annealing.
图 6 掺PrCu磁体透射电镜明场像照片(BF)及对应区域的选区电子衍射照片、元素面分布照片 (a) 烧结态; (b) 一级回火态; (c) 二级回火态
Figure 6. Bright field image (BF) and corresponding Selected Area Electron Diffraction figure and EDX mapping of PrCu-doped magnet: (a) As-sintered; (b) 1st-annealing; (c) 2nd-annealing.
表 1 原磁体和掺PrCu磁体的室温磁性能对比
Table 1. Comparison of magnetic properties between original-magnet and PrCu-doped magnet.
剩磁Br/kGs 矫顽力Hcj/kOe 最大磁能积
(BH)max/
MGOe方形度
Hk/Hcj/%原磁体 烧结态 11.32 15.64 31.04 94.4 一级回火态 11.30 17.22 30.88 95.0 二级回火态 11.30 22.24 31.39 95.9 掺PrCu
磁体烧结态 11.31 16.34 30.89 88.9 一级回火态 11.30 17.60 30.51 89.3 二级回火态 11.30 23.53 31.36 95.1 
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表 2 掺PrCu磁体三种状态样品中不同相的元素含量
Table 2. Element content of different phases in three kinds of PrCu-doped magnets.
wt.% O Fe Co Cu Pr Nd Dy 烧结态 主相 0.89 56.185 13.14 0.31 4.87 15.32 9.28 贫Co相 4.02 4.63 1.98 1.13 24.68 56.75 6.83 富Co相 0.96 20.54 23.62 0.47 13.66 34.62 6.14 一级
回火态主相 0.93 56.74 13.24 0.38 4.6 14.87 9.24 贫Co相 4.79 2.67 1.79 1.61 25.37 56.98 6.79 富Co相 1.15 11.72 16.01 0.58 20.15 44.2 6.19 二级
回火态主相 0.81 56.23 13.89 0.3 4.86 14.78 9.14 贫Co相1 2.21 5.61 9.02 1.47 23.86 51.67 6.16 贫Co相2 2.03 6.16 4.05 1.52 25.39 54.54 6.31
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[1] Sagawa M, Fujimura S, Togawa N, Yamamoto H, Matsuura Y 1984 J. Appl. Phys. 55 2083
Google Scholar
[2] Yan G L, McGuiness P J, Farr J P G, Harris I R 2010 J. Alloys Compd. J. Alloys Compd. 491 L20
Google Scholar
[3] Mottram R S, Williams A J, Harris I R 2000 J. Magn. Magn. Mater. 217 27
Google Scholar
[4] Hu Z H, Lian F Z, Zhu M G, Li W 2008 J. Magn. Magn. Mater. 320 2364
Google Scholar
[5] Kostyuchenko N V, Tereshina I S, Gorbunoy D I, Tereshina-Chitrova E A, Rogacki K, Andreev A V, Doerr M, Politova G A, Zvezdin A K 2020 Intermetallics 124 106840
Google Scholar
[6] Cui X G, Yan M, Ma T Y, Luo W, Tu S J 2009 Sci. Sinter. 41 91
Google Scholar
[7] Brown D, Ma B M, Chen Z M 2002 J. Magn. Magn. Mater. 248 432
Google Scholar
[8] Yan M, Yu L Q, Luo W, Wang W, Zhang W Y, Wen Y H 2006 J. Magn. Magn. Mater. 301 1
Google Scholar
[9] Li W F, Ohkubo T, Hono K 2009 Acta Mater. 57 1337
Google Scholar
[10] 李栋, 董生智, 李磊, 徐吉元, 陈红升, 李卫 2020 物理学报 69 147501
Google Scholar
Li D, Dong S Z, Li L, Xu J Y, Chen H S, Li W 2020 Acta Phys. Sin. 69 147501
Google Scholar
[11] Kim A S, Camp F E 1996 J. Appl. Phys. 79 5035
Google Scholar
[12] Pandian S, Chandrasekaran V, Markandeyulu G, Lyer K J L, Rao R 2002 J. Appl. Phys. 92 6082
Google Scholar
[13] Ni J J, Ma T Y, Yan M 2011 J. Magn. Magn. Mater. 323 2549
Google Scholar
[14] Li M, Tamura T 2021 J. Alloys Compd. 883 160915
Google Scholar
[15] Luo S E, Lu Y J, Zou Y R, Zhong S W, Wu Y, Yang M N 2021 J. Magn. Magn. Mater. 523 167620
Google Scholar
[16] 张家滕, 徐吉元, 胡成林, 孟睿阳, 董生智 2022 中国稀土学报 40 235
Zhang J T, Xu J Y, Hu C L, Meng R Y, Dong S Z. 2022 J. Chin. Rare Earth Soc. 40 235
[17] 胡伯平, 饶晓雷, 王亦忠 2017 稀土永磁材料(上册) (北京: 冶金工业出版社) 第197页
Hu B P, Rao X L, Wang Y Z 2017 Rare-earth Permanent Magnet Materials (Vol. 1) (Beijing: Metallurgical Industry Press) p197 (in Chinese)
[18] Kou X C, Zhao T S, R. Grössinger, de Boer F R 1992 Phys. Rev. B 46 6225
Google Scholar
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