快淬NdFeB磁粉磁性能不均匀性问题的研究

Ununiformity of Magnetic Properties for Melt-Spun NdFeB Powder

用磁选方法从同一批生产的含合金元素Zr和Co的快淬NdFeB磁粉中选出磁性能明显不同的优劣两种粉磁,研究优劣两种磁粉的成分及显微组织结构差别。结果表明:优质磁粉的Zr含量明显偏低、Fe含量略高,晶粒结晶完整、晶界衬度清晰,晶界上无其它相存在,晶粒尺寸大都分布在20～60nm范围内,较为均匀;而劣质磁粉的Zr含量偏高、Fe含量稍低,且劣质粉中存在大量的亚稳态组织结构,包括非晶、α-Fe+非晶以及≤10nm衬度不清晰、结构不完整的Nd2Fe14B晶粒。认为,劣质磁粉中含Zr量偏高,提高了发生晶化的开始温度是造成磁性能不均匀的主要原因。

Superior and inferior magnetic powders can be separated from the same batch crystallined NdFeB magnetic powders containing Zr and Co elements by magnetic separation method due to their magnetic ununiformity. The compositions and microstructures of the two powders with different magnetic properties were investigated. The results show that the superior powders contain less Zr and a relative more Fe, with integrated grains of about 20-60 nm in size and clear grain boundary without other phases. And the inferior powders contain more Zr and a relative lower Fe and metastable microstructures including the amorphous phases, the α-Fe and amorphous phases, and the un-integrated Nd2Fe14B phases of ≤ 10 nm in size. It is presumed that the ununiform magnetic properties are due to the elevated crystallization temperature induced by the more Zr content for the inferior powders.