Sm_2Co_(17)型高温稀土永磁的微结构与磁性能

Microstructure and coercivity mechanism of Sm_2Co_(17) type high temperature rare-earth permanent magnets

采用透射电子显微镜(TEM)、扫描电子显微镜(SEM)、磁力显微镜(MFM)和原位X射线衍射(XRD)等探讨Sm2Co17型稀土永磁材料的胞状结构、畴结构和相结构及其对磁性能的影响,制备使用温度为500℃的高温稀土永磁材料。结果表明,Sm(CoFe0.11Cu0.10Zr0.03)7.5具有很好的高温稳定性,500℃时的磁性能为:Br=0.708 T,Hci=646.7 kA/m,BHmax=85.4 kJ/m3;其磁畴宽度远小于晶粒尺寸,但大于胞状结构的尺寸,使用温度较高的磁体具有较小的磁畴和胞状结构;当使用温度小于300℃时,Sm2Co17型磁体内存在的相结构为2:17R、2:17H和1:5相,矫顽力主要受1:5相的钉扎而产生;当300℃<t<tc1:5时,部分1:5相转变成中间相并最终转变成2:7相,磁体的矫顽力将由1:5相钉扎和2:7相形核所控制;当t≥tc1:5时,磁体的矫顽力将全部由非磁性1:5相和2:7相形核所控制。

High temperature Sm2Co17-based permanent magnets used at 500 ℃ were attained and the cellular structure, domain structure and crystalline phase were investigated by transmission electron microscopy （TEM）, scaning electron microscopy （SEM）, magnetic force microscopy （MFM） and in-sute X-ray diffractometry. Sm（CoFe0.11Cu0.10Zr0.03）7.5 shows better high temperature properties at 500℃ with Br=0.708 T, Hci=646.7 kA/m, BHmax=85.4 kJ/m^3. It is discovered that the domain spacing is much smaller than the grain size and larger than the cellular structure. The magnet used at higher temperature shows smaller domain spacing and cell size. When the temperature is lower than 300℃, the microstructure of the magnet consists of 2：17R phase, 1：5 phase and lamella phase, and the the 1：5 phase acts as a barrier for domain wall displacements. In the intermediate temperature range （300℃ 〈t〈tc^1：5）, a part of 1：5 phase transform to 2：7 phase, and the coercivity mechanism changes to pinning at the 1：5 phase and nucleation at the 2：7 phase. With increasing the temperature higher than the Curie temperature of the 1：5 cell walls a nucleation mechanism at the 1：5 non-magnetic phase and 2：7 phase may be dominant.