Cu-added jelly-roll Nb3Al superconductor with various Nb/Al spacings and compositions

Rapid-heating, quenching, and transformation (RHQT)-processed Nb₃Al was found to provide high critical current density in high field by Cu addition. There seems to be a difference in the reaction path to A15 between binary Nb/Al (non-Cu-addition) and the Cu added ternary. In the binary case, a Nb/Al composite reacted to form a bcc phase through rapid-heating and quenching (RHQ) treatment and then it was transformed into A15 phase including stacking faults by an 800 °C heat treatment. On the other hand, when Cu was added, the composite reacted to form A15 phase including stacking faults through RHQ treatment directly. We fabricated Cu added jelly-roll (JR) Nb/Al wire with various Nb/Al layer thicknesses and compositions and investigated their effect on RHQ process. The Cu added JR wire of Al poor composition for Nb₃Al stoichiometry showed a behavior similar to the binary. Al rich composition showed a behavior similar to the Cu-addition case. In this work we discussed the Cu addition effect by considering these results.