Reel-to-Reel Heat Treatment, Microstructure, and Superconducting Properties of Jelly-Roll Nb3Al Superconducting Wire

In this work, we utilized the jelly-roll method to make a single-filament Nb3Al precursor long wire, combining with a homemade reel-to-reel rapid heating and quenching (RHQ) equipment, and consequently the high-performance Nb3Al superconducting wires had been prepared. By investigating the heating current and wire moving speed, the optimized RHQ heat treatment conditions of this Nb3Al wire were obtained. The results suggest that the Tc for the Nb3Al superconducting wire is up to 17.4 K and the non-Cu critical current density (non-Cu Jc) reaches 1238 A/mm2 at 4.2 K and 12 T, which indicates the bcc-phase Nb–Al supersaturated solid solution has already been generated. Considering the Nb3Al precursor wire with a large thickness of Al layer, about 690 nm, such high Jc is quite unexpected. The SEM analysis presents that there is still some unreacted Nb and Nb2Al phase in the superconducting wire, which may result from the inhomogeneity of Nb and Al foils. This work implies the Nb3Al superconducting wire is promising to the application of high-field superconducting magnets.