Cu-additional effects on RHQ-processed Nb3Al multifilamentary superconductors

Cu-additional effects have been investigated on the rapid heating, quenching, and transforming (RHQT)-processed Nb3Al multifilamentary wire. When the Nb/Al-(2-5)at.%Cu microcomposite wire was rapidly heated and quenched (RHQ-treatment), disordered A15 phase filaments were formed directly instead of Nb-Al bee supersaturated phase filament formation in the normal RHQT-process. With annealing at 700-800 C, its superconducting properties were improved. The 2 at.%Cu-added Nb3Al multifilamentary wire showed the maximum values of T-c = 18.4 K and H-c2 (4.2 K) = 29.7 T, which are higher than the maximum values of T-c = 17.8 K and H-c2 (4.2 K) = 26.3 T for the RHQT-processed Nb3Al wire without Cu addition. However, the 5 at.%Cu-addition showed a little degradation in the superconducting properties of Nb3Al wire. With reducing the moving velocity of RHQ-treatment down to 0.4 m/s, the J(c)(4.2 K) of 2 at.%Cu-added wire was improved significantly up to 1000 A/mm(2) at 19 T and 400 A/mm(2) at 23 T, which are the highest reported values among the multifilamentary metallic superconductors. (C) 2002 Elsevier Science B.V. All rights reserved.