低温超导体Nb_3Sn扩散热处理中显微组织的表征与分析

Characterization and Analysis of Microstructures of Nb_3Sn Multifilamentary Superconductors during Diffusion Treatment by Bronze Route

利用青铜法制备了低温超导体Nb3Sn材料。采用X射线衍射(XRD),扫描电镜(SEM)和能谱(EDS)对Nb3Sn化合物的元素扩散热处理过程进行了研究。结果显示,通过热处理96h后,Nb3Sn相形成。同时由于边界处Nb原子的缺乏,Nb2Sn和Nb6Sn5非超导相也在边界处形成。升高温度明显能够提高元素的扩散激活能,从而利于Nb3Sn相的形成,但是高温也会促进晶粒的粗化,破坏超导特性。因此精确控制温度对于材料超导性能非常重要。采用670℃热处理96h得到了均匀细小的晶粒组织。

The element diffusion process of Nb3Sn multifilamentary superconductors fabricated by bronze route was studied using X-ray diffraction （XRD）, scanning electron microscopy （SEM） and energy disperse spectroscopy （EDS）. The results showed that the superconductive Nb3Sn phase was formed after the heating time was longer than 96 h. At the same time, NbSn2 and Nb6Sn5 also appeared because of the local clustering of Sn atoms. Increasing heat-treatment temperature might increase the active energy of Sn atoms diffusion, which was beneficial to form Nb3Sn phase. But the grain coarseness would take place in the condition of high temperature, which was harmful to the superconductivity. Therefore, it is very important for improvement of the superconductivity of samples to control the temperature. In this study, the fine grain structured Nb3Sn multifilamentary superconductors heated at 670 ℃ for 96 h were fabricated successfully.