真空退火提髙薄型磁体性能的研究

Study to improve magnetic properties of thin magnets by vacuum annealing

机加工成一定尺寸和形状的烧结NdFeB薄型磁体,由于表面晶粒形变和缺陷的产生引起了磁性能的降低,适当的真空退火热处理后,其磁性能将会得到恢复和提髙。通过SEM扫描电镜,X射线衍射和磁性能的测量,研究了退火热处理对磁体表面层晶粒微结构、应变、亚晶粒尺寸和磁性能的影响。结果表明,在三相共晶点温度以上,900℃×2h+490℃×5h的退火可以完全消除机加工产生的应変、应力和缺陷。其次,表面层内晶界富Nd相的毛细管作用和扩散迁移,使富Nd相均匀、连续地分布在晶粒和晶界周围。这种富Nd相网状结构,消除了机加工磁体表层内的晶界裂纹和缺陷,对磁体性能的恢复和提高起着重要的作用。

In the article we have done the research on the influence of the annealing treatment on the surface grains＇ strain,micro-structure,sub-crystallite size and magnetic properties of the thin NdFeB magnet by ordering the SEM scanning electron microscope,X-ray diffraction and magnetic property measurement.The results showed that： firstly,above the three-phase eutectic temperature,900℃×2h＋490×5h of annealing treatment can completely eliminate machining strain,stress and defects.Secondly,the capillary action and diffusion of the grain boundary Nd-rich phase uniformly and continuously distributed in the grains and grain boundary around.The Nd-rich phase of this network structure eliminated the grain boundary cracks and defects,and played an important role on the magnetic properties recovery and improvement.