Properties of high strength Cu-Nb conductor for pulsed magnet applications

Various tests have been undertaken to study the effects of annealing, testing temperatures and volume fraction of the Cu cladding on the properties of Cu-Nb conductors being developed for pulsed magnet applications. The results demonstrate that short time annealing used for insulation had no significant effect on the tensile property of Cu-Nb conductors. The cryogenic temperatures are beneficial to both the conductivity and mechanical properties of the conductors, especially the tensile strength of the Cu cladding. The wire-drawing fabrications showed that wires of 4 mm x 6 mm cross-section-area with a significant volume fraction of Cu cladding could be obtained, leading to final tensile strengths of up to 1100 MPa at room temperature. The strength is increased by about 20% at 77 K. The 77 K-conductivity is about 4.5 times of the room temperature one. The strengthening mechanisms and resistivity variation of the Cu-Nb composite are discussed and it is argued that the distance between the Nb ribbons plays an important role in the variation of these properties.