电阻焊接技术制备Nb3Sn-NbTi 混合超导接头

Preparation of Nb3Sn-NbTi Hybrid Superconducting Joint by Resistive Welding Technique

摘要:

在强磁场超导磁体应用中，特别是具有高稳定度高场超导磁体，具有极低电阻的超导接头发挥着重要作用。通过电阻焊接方法制备了Nb₃Sn 和NbTi的异种材料超导接头。首先通过烧结法制备了Nb₃Sn的超导接头，然后通过电阻焊接将Nb₃Sn超导接头与NbTi超导体焊接成型。分析了Nb₃Sn超导接头制备过程中Nb₃Sn的微观组织结构和相变。利用无损检测CT对接头结构进行三维重构，分析了Nb₃Sn 和NbTi超导接头内部的缺陷和2种不同材料间的微观连接状态。最后，在背景磁场下对超导接头的电阻性能进行了测试和研究。结果表明，与传统超导焊料制备的超导接头相比，电阻焊接制备的超导接头显示出良好的耐磁场性能，在1.5 T背景磁场下具有较低的电阻值。

Abstract:

In high magnetic field magnets, especially those with high stability requirements, superconducting joints with ultra-low resistances play an important role in magnet fabrication. The Nb₃Sn and NbTi joints were fabricated by the resistive welding technique. The Nb₃Sn joint was fabricated by sintering the Nb-Sn precursors after mechanical alloying. Then the Nb₃Sn bulk in the Nb₃Sn joint was welded to the NbTi conductor. The microstructure and grain sizes of Nb₃Sn bulk after long periods of time at high temperature were investigated. After welding, the joint was analyzed using X-ray nano-CT technology to display the connecting status and the defects between the Nb₃Sn and NbTi conductor without destroying the joint. The electrical characteristics of the joints were measured under background fields through the field decay method. Results show that compared with the ones prepared by the commonly used solid matrix replacement technique, the prepared joint exhibits better magnetic field resistance and lower resistance at 1.5 T background field.