Reproducible stable critical current density in powder-in-tube (PIT) Nb3Al superconductors by multi-time rapid heating and quenching process

Abstract

This paper investigated the microstructure and superconductivity of the powder-in-tube (PIT) Nb3Al short samples with different rapid heating and quenching (RHQ) treatment. Single RHQ processed Nb3Al wires showed inhomogeneous microstructure and the superconductivity were sensitive to rapid heating temperature (Tmax), showing significant fluctuation with a slight change of Tmax. Multi-time RHQ treatment was performed to homogenize the Nb3Al superconductors. The highly uniform microstructure and composition distribution were found in 5-time RHQ processed Nb3Al wires, which exhibited significantly stable and excellent Jc performance. Reproducible stable Jc results of Nb3Al wires were realized in three samples of 5-time RHQ treatment with a difference of Tmax reaching about 200 °C. Jc of the three samples fluctuated less than 20% with results of 1.1 × 105 A/cm2, 9.87 × 104 A/cm2 and 9.51 × 104 A/cm2 at 4.2 K and 12 T. The insensitivity of Jc to Tmax in 5-time RHQ processed Nb3Al samples might attribute to the highly homogeneous Nb3Al A15 phase.