Phase Structure and Superconducting Properties of RHQT Nb3Al Wires Fabricated by Static and Dynamic Rapid Heating

This work compared the phase structure and superconducting properties of Nb3Al wires fabricated by static and dynamic rapid heating and quenching (RHQ) process. Single A15 Nb3Al phase was formed in transformed wires under rapid heating current (IRHQ) from 67 A to 69 A and from 120 A to 123 A for static and dynamic RHQ operation. The Tc-onset of RHQT Nb3Al wires are sensitive to IRHQ. Dynamic RHQT Nb3Al wires show much narrower ΔTc (~1.1 K) than that of static samples (>2.1 K), indicating better uniformity of the Nb3Al phase. Critical current density (Jc) at 4.2 K, 6.5 T of the single phase Nb3Al wires ranges from 4.7 × 10
⁴
to 6.9 × 10
⁴
A/cm
²
for the dynamic RHQ samples, and ranges from 1.5 × 10
⁴
to 3.4 × 10
⁴
A/cm
²
for the static RHQ wires. The precursor wires operated at other IRHQ conditions, that was below 65 A for static RHQ and 124 A for dynamic RHQ, exhibit much lower Jc results for including of Nb2Al impurity phase in the Nb3Al wires. The Birr reaches maximum values of 19.5 T and 19.1 T at 4.2 K, 10.5 T and 11.8 T at 10 K for the best static and dynamic RHQT Nb3Al wires. The main pinning mechanism of Nb3Al superconductor was surface pinning where grain boundaries or stacking faults acted as the pinning centers.