磁场凝固法制备过共晶MnBi/Bi磁性功能复合材料

Fabrication of hypereutectic MnBi/Bi magnetic functional composites by solidification in a magnetic field

Bi Mn过共晶合金分别从3个不同状态凝固,合金中MnBi析出相均在磁场作用下以晶体的c轴平行磁场取向,形成规则排列组织,并且所得材料的剩磁都具有明显的各向异性。合金从低于355℃的固液两相区凝固时,铁磁性MnBi析出相在1.0T磁场中迅速形成均布的织构组织,并能在无磁场条件下保持稳定,材料无需热处理就有很好的剩磁性能。因此,磁场凝固技术能够高效率地、直接制备出性能优良的MnBi/Bi磁性功能复合材料。

Three different kinds of solidification process of hypereutectic Bi-Mn alloys with a magnetic field applied have been investigated. There are alignment microstructure of MnBi precipitated phase in the alloys oriented with their crystallographic c-axis parallel to the direction of the field in all these cases. The remnant magnetism of the alloys crystallized in the field is found to be strongly anisotropic. When Bi-Mn alloys were solidified from a temperature in the mushy zone below 355°C with 1. 0T, rapid formation and uniformed distribution of textured ferromagnetic MnBi phase occurred in the alloys and the structure was proved to be stable without a magnetic field applied. Moreover, the remnant magnetism of the alloys solidified in this process was well and no heat treatment was required. Therefore, MnBi/Bi functional composites with excellent magnetic properties could be prepared directly with high efficiency by solidification in a magnetic field.