Maximization of the critical current of practical Nb_3Sn wires through complex mechanical treatments at room temperature

摘要

Relaxation of the thermal residual strain in Nb_3Sn wires is realized through cycles of multiple torsion loadings ('pre-torsion') at room temperature. As a consequence, the critical current, I_c, is enhanced. This effect is stronger than previously reported mechanical treatments of multiple bending ('pre-bending'). The maximum I_c is attained for complex mechanical treatments of pre-torsion and pre-bending. Complex treatments allow efficient and relatively independent control of residual strain relaxation over all three directions of the wire, resulting in enhancement of I_c towards the theoretical limit of the material. Our findings have an immediate positive impact on the performance of Nb_3Sn wires and, hence, on their applications (e.g. react-and-wind coils).