高电阻率高矫顽力DyF₃/NdF₃夹层钕铁硼复合磁体研究

Research on High Resistivity and High Coercivity DyF₃/NdF₃ Interlayered NdFeB Composite Magnets

摘要: 为了提高钕铁硼磁体的电阻率，降低其在高频高速永磁电机工作时的涡流损耗和温升，本文采用热压热变形工艺制备了含DyF₃/NdF₃复合绝缘夹层的高电阻率钕铁硼磁体，研究了绝缘夹层成分、含量及热变形温度对磁体微观结构、磁性能、电阻率和抗弯强度的影响。结果表明，随着DyF₃/NdF₃含量或者NdF₃占比的增大，夹层钕铁硼复合磁体的电阻率逐渐提高，当DyF₃/NdF₃比例为1:5、含量为6.52 × 10⁻⁴ g/mm²时，磁体电阻率最高，为11.5 mΩ·cm。当DyF₃/NdF₃比例为1:5、1:3时，磁体抗弯强度随添加量的增加呈先下降后增加变化，复合粉体以1:1、3:1比例添加时，磁体抗弯强度也是整体降低，但随添加量的增加呈波动性变化。DyF₃/NdF₃含量越高，对磁体的性能影响越大，但是夹层钕铁硼复合磁体的矫顽力(H_cj)都比较高，最低也接近10 kOe。当DyF₃/NdF₃比例3:1、含量为3.26 × 10⁻⁴ g/mm²时，复合磁体最大磁能积(BH)_max最高，为46.47 MGOe。热变形温度对夹层钕铁硼复合磁体的磁性能和电阻率影响较大，在825℃热变形制备的夹层钕铁硼复合磁体的矫顽力最高，为15.6 kOe，在850℃热变形制备的夹层钕铁硼复合磁体的剩磁B_r、(BH)_max和电阻率最大，分别达到了13.42 kGs、42.95 MGOe和9.37 mΩ·cm。

Abstract: In this paper, in order to enhance the resistivity of NdFeB magnets and reduce their eddy current losses and temperature rise during operation in high-frequency and high-speed permanent magnetic motors, high-resistivity NdFeB magnets with DyF₃/NdF₃ composite insulating interlayers through hot-pressing and hot-deformation processes have been fabricated. The effects of insulating interlayer composition, amount, and hot-deformation temperature on the microstructure, magnetic properties, resistivity and bending strength of the magnets are systematically investigated. The results show that as the DyF₃/NdF₃ amount or NdF₃ proportion increases, the resistivity of the interlayered NdFeB composite magnets gradually increases. When the DyF₃/NdF₃ ratio is 1:5 and the amount is 6.52 × 10⁻⁴ g/mm², the resistivity of the magnets reaches a maximum of 11.5 mΩ·cm. When the DyF₃/NdF₃ ratio is 1:5 or 1:3, the overall bending strength of the magnet initially decreases and then increases as the addition’s amount increases. When the DyF₃/NdF₃ ratio is 1:1 or 3:1, the magnet’s bending strength also generally decreases, but fluctuates with the increase of the addition’s amounts. The higher the DyF₃/NdF₃ content, the greater the impact on the magnetic properties of the magnets, but the coercivity, H_cj, of the interlayered NdFeB composite magnets is relatively high, with a minimum value close to 10 kOe. When the DyF₃/NdF₃ ratio is 3:1 and the content is 3.26 × 10⁻⁴ g/mm², the maximum magnetic energy product, (BH)_max, of the composite magnets reaches a maximum of 46.47 MGOe. The hot-deformation temperature has a significant impact on the magnetic properties and resistivity of the interlayered NdFeB composite magnets. The coercivity of the interlayered NdFeB composite magnets hot-deformed at 825˚C reaches a maximum of 15.6 kOe, while the remanence, B_r, (BH)_max and resistivity of the interlayered NdFeB composite magnets hot-deformed at 850˚C are the highest, reaching 13.42 kGs, 42.95 MGOe and 9.37 mΩ·cm, respectively.