Nb/sub 3/Al conductors-rapid-heating, quenching and transformation process

Abstract

An outline of the Nb/sub 3/Al conductor prepared by rapid-heating, quenching and transformation (RHQT) process is described, together with that of Nb/sub 3/Al conductors fabricated by other process. The RHQT process produces highly stoichiometric Nb/sub 3/Al with fine grains, via supersaturated-solid solution Nb(Al)/sub ss/. The RHQT Nb/sub 3/Al exhibits a quite high critical current density J/sub c/ over the whole range of magnetic fields, in particular, in fields above 20 T. The achieved high stoichiometry accounts for the substantially improved high field performance and is compatible with the excellent strain tolerance which makes Nb/sub 3/Al superior over Nb/sub 3/Sn conductors. Deformability of as-quenched Nb/Nb(Al)/sub ss/ is enough for the conductor to be externally stabilized with Cu, stranded to a cable, flat-roll formed and wound to a coil, before transforming Nb(Al)/sub ss/ to A15-type Nb/sub 3/Al. The current carrying capacity has been enhanced through increasing wire diameter and reduced Nb matrix ratio. Incorporation of stabilizer has been externally and internally made for RHQT JR Nb/sub 3/Al conductors.