用双合金工艺在 (Nd0.75Dy0.10Tb0.15)12.69Fe79.01Co2.00Nb0.30B6.00 近正分主合金粉中添加质量分数为3%的富稀土辅合金 (Nd0.75Dy0.10Tb0.15)25.00Fe21.50Co21.50Nb4.00Ga8.00Ti5.00Al8.00B7.00粉 和3 %的Dy2O3粉, 成功制备出超高矫顽力和高热稳定性的烧结Nd-Fe-B磁体, 内禀矫顽力 Hci和最大磁能积(BH)max分别为3028 kA/m和 254 kJ/m3, 22-220 ℃剩磁和矫顽力的温度系数 分别为--0.104%℃和--0.356%℃, 260 ℃不可逆磁通损失L irr的绝对值仅为4%。微观组织分析表明: 主相Nd2Fe14B晶粒边界光滑、平直, 富Nd相连续均匀分布于主相晶粒周围; 在Nd2Fe14B晶粒 表层附近富含Dy, Dy2O3中的Dy通过扩散与富Nd相及Nd2Fe14B晶粒表层中的Nd发生置换, 从而在界面附近增强了磁各向异性. 在此基础上, 进一步提出了制备高矫顽力烧结Nd-Fe-B 磁体中Dy的理想分布示意图.
Sintered Nd-Fe-B magnet with super-high coercivity and high thermal stability was achieved by blending 3wt%Dy2O3 powder and 3wt% (NdDyTb)25(FeCoNbTiGaAl)68B7 powder to near stoichiometric (NdDyTb)12.69(FeCoNb)84.01B6.00 main alloy powder. The intrinsic coercivity Hci with 3028kA/m, the maximum energy product (BH)max with 254 kJ/m3, the temperature coefficient (22-220℃) of remanence and intrinsic coercivity with -0.104%/ ℃ and -0.356%/ ℃, respectively, and irreversible flux loss at 260℃ near 4% were accomplished. Microstructure analyses indicated that that Nd2Fe14B grain boundaries were smooth and straight and the distribution of Nd-rich phase around Nd2Fe14B grain was continuous and uniform. Dy was rich in near the extension layer of Nd2Fe14B grains, indicating Dy element in Dy2O3 powder diffused and substituted Nd element in Nd-rich phase and the extension layer of Nd2Fe14B grains, which increased magnetic anisotropy of boundary of Nd2Fe14B grains only and depressed the nucleation formation and expansion of reverse magnetization domain. Furthermore, ideal microstructural model of Dy distribution in Nd-Fe-B sintered magnets with high intrinsic coercivity was presented.
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