Design of Transformation-Processed $\hbox {Nb}_{3} \hbox {Al}$ Conductors to Balance Drawability and Inter-Filament Decoupling

Transformation-processed Nb₃Al superconductors should be used in conjunction with a high-melting-point matrix material such as Nb. However, Nb is superconductive below 9 K, which causes low-field instability due to magnetic interfilament coupling at liquid He temperature. One alternative matrix material is Ta. However, the use of Ta sacrifices the drawability of the precursor wires, increasing the risk of wire breakage during drawing. In this work, a new layout intended to balance drawability and interfilament decoupling is proposed. In this new layout, Nb barrier filaments are concentrated around the central dummy core, and Ta barrier filaments are located so as to magnetically decouple the Nb barrier filaments in the outer filamentary region. The drawability and magnetization behavior of the newly designed Nb₃Al wires are compared with those of conventional wires.