Monitoring of intermetallic phase formation in jelly-rolled Nb/Al multifilamentary conductors by in-situ resistometry

In-situ resistance measurements were performed on jelly-rolled Nb/Al multifilamentary conductors during solid-state diffusion at temperatures less than 850 °C. During the heat treatment, formation of NbAl3 and Nb3Al phases can be clearly identified in the plot against temperature of the first derivative of resistivity with respect to temperature (dρ/dT). In addition, the two-stage formation of a single phase (NbAl3) is also observed in the dρ/dT plot. The superconducting properties of the A15 Nb3Al phase were measured after different heat treatments, and were found to be approximately independent of the extent of NbAl3 formation at low temperatures.