高场磁体用 Nb3Al 超导线材研究进展

摘要

Nb3 Al 超导体的超导转变温度（Tc ）和上临界磁场（Hc2）与 Nb3 Sn 类似，但具有更好的应力应变容许特性和高场临界电流密度（Jc ）。因此，被认为是下一代高场磁体应用的理想材料。目前国际上报道的 Nb3 Al 超导线材单根长度可以达到2.6 km；在4.2 K 和15 T 条件下，Jc 达到1000 A ／mm2；但是由于制备工艺的复杂性，目前仍然无法实现大规模工业化应用。首先阐述了 Nb3 Al 超导材料的基本特性，如 Nb ／Al 扩散间距小、二者硬度匹配性小和低温热处理导致 Al 含量偏离化学计量比等，以及由此带来的材料加工和热处理方面的难点；系统介绍了近年来针对 Nb3 Al 超导长线性能提升，在前驱体制备工艺、热处理工艺和表面覆 Cu 工艺方面的研究进展，并对不同的工艺进行了比较分析，重点讨论了线材制备过程中存在的关键性难点问题；最后，对 Nb3 Al 超导材料的发展趋势进行了展望。%The superconducting transition temperature (Tc )and upper critical magnetic field (Hc2 )of Nb3 Al supercon-ductor are similar to Nb3 Sn,but it has better strain tolerance and higher critical current(Jc )at high field.Therefore, Nb3 Al superconductor is considered as a very appealing material for use in future high field application.At present,the Nb3 Al superconducting wire with 2.6 km long length had been reported,which exhibited a large Jc of 1 000 A /mm2 at 4.2 K and 15 T.Due to the complexity of fabrication techniques,it can not be commercially applied.In this paper,the basic properties of Nb3 Al are introduced,such as little diffuse space,large difference in hardness and off-stoichiometric with low temperature heat-treatment.Besides,various precursor fabrication,heat-treatment and Cu cladding techniques are described and compared,and the difficulties of fabrication,processes are analysed especially.In the end,a perspec-tive and future development of Nb3 Al superconductor are given.