快淬粉爆炸压制Nd-Fe-B永磁体的性能与结构特征

CHARACTERIZATION OF MELT-SPUN Nd-Fe-B MAGNETS PREPARED BY EXPLOSIVE COMPACTION

利用爆炸压制方法制备的快淬永磁体,其磁性能、压缩强度和密度都比相同粉料制备的粘结磁体有明显提高,其中最大磁能积(BH)max提高了30%,压缩强度bσc增加了40%。扫描电镜观察显示,爆炸压制磁体的粉体颗粒表面出现了局部的熔融区域与大量的微裂纹。借助于场发射扫描电镜进一步观察发现,爆炸样品粉体颗粒表面出现纳米数量级的蜂窝状组织。磁力显微镜观察表明,爆炸压制不仅保持了原始粉末细小的晶粒尺寸,还保持了原始快淬粉细小的磁畴结构,磁体粉体颗粒中存在大量的微裂纹,但是微裂纹对快淬粉爆炸压制磁体的磁性能几乎没有影响。

Explosive compaction processing is applied to prepare Nd-Fe-B magnets with melt-spun powders. It is found that shock consolidation processing could result in the magnetic properties, compressed strength and density of Nd-Fe-B bulk better than that of the conventional resin-bonded magnet. Scanning electron microscope （SEM） observation shows the melted areas and a mass of the micro-cracks in the close-packed particles resulted from the shock wave. The small Nd2 Fe14 B grains less than 100 nm are revealed using the field emission scanning electron microscope （FE-SEM）. The corresponding magnetic structure consisting of the very fine magnetic domains is also revealed with magnetic force microscopy （MFM）. The results indicate that not only the microstructure but also the magnetic domain structure of the original powder are kept after explosive compaction. Although there are many micro-cracks in particles, the excellent magnetic properties are still obtained because the magnetic domain structure is so fine that seems not to be affected by the micro-cracks.