Fe-Zr-B系纳米晶材料的微结构和磁性

MICROSTRUCTURES AND MAGNETIC PROPERTIES OF Fe-Zr-B BASE NANOCRYSTALLINE ALLOYS

综合利用原子探针、透射电镜和高分辨电镜在原子尺度上研究了Fe-14B中B和FeZrB中添加元素Cu、Au和Si的分布及其对磁性的影响。主要结果有:(1)对Fe-14B,直径约为80 nm的α-Fe中B含量高达2.5 at％,这是α-Fe与非晶富B相平衡的结果;(2)加入Cu后Cu原子在α-Fe结晶以前形成Cu原子团簇,为α-Fe相提供形核位置,提高其形核密度;(3)加入Au后,在形成较多的α—Fe以后Au才形成团簇,在α-Fe长大过程中Au和Zr发生共偏聚;(4)对加Si非晶,在α-Fe的形核和长大期间,Si原子被从α-Fe中排除进入非晶相,Si的加入使α-Fe的体积分数下降,因而使磁致伸缩系数λS增加,Si含量为4at％时,λS=0。上述结果为设计高性能纳米晶软磁材料提供了科学依据。

We have studied the partitioning of B in Fe-14B and the partitioning of Zr, B, Si, Cu and Au in FeZrB nanocrystalline soft magnetic alloys by using atom probe field ion microscopy (APFIM) and high resolution microscopy (HREM) in atomic or nanometric scale and the effect of Si, Cu, Au additions on the magnetic properties. For Fe-14B after annealing, a-Fe particles with diameter of about 50-100 nm formed and they contain highly supersaturated B. For Fe-7Zr-3B-lCu amorphous alloy, it was found that Cu atoms formed clusters prior to the crystallization reaction. During the crystallization Cu enriched clusters provided nucleation sites for a-Fe phase so that the nucleation density of a-Fe phase is increased. For Fe-7Zr-5B-lAu amorphous alloy, Au clusters were observed during the nucleation and growth stage of primary a-Fe and a-Fe particles did not form at the site of Au cluster. Hence Au does not enhance the nucleation density of a-Fe particles. For Fe-7Zr-4Si-2B alloy it is found that Si atoms are rejected from a-Fe primary crystals and partitioned into the residual amorphous phase. This result suggests that Si addition does not cause reduction in inherent magnetostriction of a-Fe nano particles, but it brings the volume fraction of the a-Fe particles to an optimum value so that the average megnetostriction becomes zero. This conclusion has been strengthened by comparing the changes in magnetostriction constants as a function of Si content in Fe-Zr-Si-B alloys.