Superconducting Properties of Jelly-Roll Nb3Al Short Wire Prepared by Rapid Heating, Quenching, and Transformation Method

A multifilamentary Nb/Al precursor is fabricated by the jelly-roll process method. The final diameter without Cu is 0.6 mm. The final Al layer is 200-300 nm in thickness. An apparatus is designed and constructed to perform the rapid heating and quenching (RHQ) treatment for the Nb/Al precursor short samples. After the RHQ treatment, the short samples are heat treated at 800 °C for 10 h. Transport tests and magnetization measurements are performed at temperatures above 8 K to investigate the superconducting properties and microstructure of the samples. The highest onset TC of the samples is 17.7 K by zero-field-cooled magnetization test, which means that near-stoichiometric Nb3Al phase is achieved. Some samples have a second superconducting transition at 12-13 K. Results from transport tests show that samples heated by a voltage of 170-175 V have better current-carrying capacity (125 A/mm2 at 11 K, self-field) and high transition temperature. Further optimization on the RHQ and transformation heat treatment process is still needed to improve the superconducting properties of the samples.