Prebending Effect for Mechanical and Superconducting Properties of Nb-Rod-Processed Cu-Nb Internal-Reinforced Nb₃Sn Wires

We are planning to develop three large superconducting magnets, using CuNb-reinforced Nb3Sn Rutherford cables with the prebending treatment. CuNb-reinforced Nb3Sn wires using a new Nb-rod-processed CuNb composite were developed for the Rutherford cables. In this study, the prebending effects for the mechanical and the superconducting properties of the Nb-rod-processed CuNb/Nb₃ Sn wire were investigated. We found that the CuNb/Nb3Sn wire with 0.8% prebending treatment had largely enhanced critical current at 4.2 K. The reduction of the n-value was observed around 0.8% prebending strain. The mechanical properties of the prebent wires were enhanced. Young's modulus and 0.2% proof stress of the wire with prebending treatment at 4.2 K are 180 GPa and 270 MPa, respectively. The residual strain was released from 0.30% to 0.15% by 0.8% prebending treatment.