Field and temperature dependences of critical current density in rapid quenched and transformed Nb3Al multifilamentary conductors

Magnetic field and temperature dependences of J(c) are measured for rapid quenched and transformed Nb3Al multifilamentary wires that were fabricated by the Jelly-roll (JR) and Rod-in-tube (RIT) processes. The J(c) in the transformed JR wire was much larger than that of conventional JR processed wires and also the transformed RIT processed wire. The scaling curve for the J(c)-B-T characteristics are given by a temperature scaling law, which agrees well with the experimental results in wide temperature and field ranges. The scaling curve enables us to evaluate J(c) at low magnetic field and low temperature, for instance, J(c) at 10 T, 4.2 K is estimated as 4700 A/mm(2). The main pinning source would be grain boundaries, because of the small grain size (several tens nm) and its high density.