高熔点纳米颗粒添加对热变形Nd-Fe-B磁体性能与微观结构的影响

Impact of nano-particles with high-melting point on magnetic properties and microstructures of hot-deformed Nd-Fe-B magnet

在快淬粉中添加WC、BN 以及ZrO2等高熔点纳米颗粒,利用热压、热变形工艺,制备出具有各向异性的Nd-Fe-B磁体。研究了不同添加物对热变形磁体磁性能、微观结构的影响。结果表明,微量纳米颗粒的添加对热变形磁体的剩磁影响不大,添加氧化物纳米颗粒会明显降低磁体矫顽力,添加碳化物纳米颗粒的磁体矫顽力都有改善,尤其是添加WC纳米颗粒之后,热变形磁体获得了最佳的综合磁性能。添加WC颗粒后,热变形磁体的剩磁温度稳定性得到改善,而矫顽力温度系数几乎不受影响。对磁化行为研究发现,添加WC纳米颗粒后,热变形磁体的可逆磁化没有出现明显峰值,表明纳米WC颗粒的添加抑制了热变形磁体内粗晶区的生长,使热变形磁体微观结构更为均匀,同时磁体内部WC富集区还观察到Fe2W新相的生成。

Anisotropic Nd-Fe-B magnets were prepared by hot deformation process. Nano-particles with high melting point, such as WC, BN and ZrO2 were mixed with the Nd-Fe-B melt-spun ribbons before hot pressing process. The effects of different additions on the magnetic properties and microstructures of the hot-deformed magnets were investigated. The results show that the variation in the remanence is not obvious after adding micro additions. Oxide?nano-particles significantly decrease the coercivity of the hot-deformed magnets, while coercivity of the magnets with carbide addition is enhanced. The optimum magnetic properties are obtained at hot-deformed magnet with WC addition. The remanence thermal stability of the magnet is improved, while the coercivity temperature coefficient is hardly affected after adding WC particles. The reversible magnetization of the magnet shows no obvious peak value after adding WC nanoparticles, indicating that the addition of WC nanoparticles inhibits the growth of coarse crystal regions in the hot-deformed magnet and makes the microstructure of the magnet more uniform. At the same time, a new Fe2W phase forms at the WC-aggregated region.