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Ningbo, China

Yan C.,CAS Ningbo Institute of Material Technology and Engineering | Yan C.,Ningbo Ketian Magnet Co. | Guo S.,CAS Ningbo Institute of Material Technology and Engineering | Chen L.,CAS Ningbo Institute of Material Technology and Engineering | And 4 more authors.
IEEE Transactions on Magnetics

Effects of partial substitution of Ce for didymium (Pr-Nd alloy, abbreviated to Di) on elevated temperature magnetic properties in sintered (Di1-xCex)27.5Dy3Al0.1Cu0.1Febal.B (wt.%, x = 0 ∼ 0.56) magnets were investigated in this paper. Temperature stability of remanence was found to decrease in Ce substitution. However, the temperature stability of coercivity was largely improved when x ≥ 0.24. Temperature dependence of magnetocrystalline anisotropy field (HA) was improved as Ce substitution. Microstructural observation and micromagnetic analysis indicated that a microstructure of magnets was modified when x ≥ 0.24. The enhancement of temperature stability of coercivity was due to the improvement of temperature dependence of HA and the modification of microstructure. © 2015 IEEE. Source

Wang Y.,Ningbo Ketian Magnet Co. | Xu F.,Ningbo Ketian Magnet Co. | Zhao H.,Ningbo Ketian Magnet Co.
Xiyou Jinshu/Chinese Journal of Rare Metals

The high performance sintering Nd-Fe-B magnet with intrinsic coercivity 1027 kA·m-3 and maximum energy product 415 kJ·m-3 was prepared by a binary powder blending technique on the industrialization product line. The magnet had strong corrosion resistance; the mass loss of the magnet was only 2.08 mg·cm-2 after 168 h under the condition of 121°C, 0.27 MPa and 100% relative humidity. The effects of main alloy strip structure on sintering magnet microstructure and magnetic performance were investigated. Owing to the low rare earth concentration of the master alloy, there were a lot of α-Fe phases near the free surface of Nd28.0Fe70Co1.0B1.0 strip cast flakes, subsequently the magnet had much aggregation of Nd-rich phase, the grain boundary was unsmooth, and then the magnet had low density of 7.45 g·cm-3, the coercivity was only 870 kA·m-1. After optimizing the strip cast flakes structure, the α-Fe phases in the strip cast flakes were suppressed and Nd2Fe14B columnar grains of about 3~4 μm were formed along the solidification direction. There was less aggregation of Nd-rich phase in the magnet, the distribution of Nd-rich phase was uniformity and the grain boundary was straight and smooth. At last, the magnet density was enhanced to 7.57 g·cm-3, the coercivity was increased to 1027 kA·m-1. Source

Wang Y.,Ningbo Ketian Magnet Co. | Xu F.,Ningbo Ketian Magnet Co. | Zhao H.,Ningbo Ketian Magnet Co.
Zhongguo Xitu Xuebao/Journal of the Chinese Rare Earth Society

A high coercivity magnet of Nd31.50FebalCo3.00Al0.2Cu0.2B1.05(%) without adding heavy rare-earth was achieved with (BH)m 352 and Hcj 1356 kA·m-1 by optimizing magnet microstructure with a new preparation routine. This new preparation routine consists of an optimized strip cast with 2~3 μm columnar grains in width and well separated by the uniformly distributed RE-rich phase, an corresponding jet milling powder with 2.68 μm and 1020℃ low sintering temperature. The grain size of the magnet was 5 μm with an clear distribution of grain boundary phase. The temperature coefficients of coercivity was -0.627%·℃-1 between 20 and 120℃, and had practical applicability at 120℃. ©, 2014, Chinese Rare Earth Society. All right reserved. Source

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