Mechanical and Thermal Properties of Central Former Material for High-Current Superconducting Cables

Ongoing projects to realize high-current superconducting cables for transport or magnet applications need to incorporate a high number of coated conductor tapes. Several design layouts published, such as conductor-on-round-core cable, stacks, or Roebel-Rutherford, can achieve this. Design layouts proposed by the research institutes ENEA and KIT use a central former having grooves along the length where stacks of tapes or Roebel strands can be embedded. The former material is a substantial fraction of the cable cross section influencing the overall performance of the cable. In this work, materials used as the central former are investigated after severe plastic deformation, using equal channel angular pressing (ECAP) and equal channel angular rolling (ECAR) processes. Applying these methods allows producing continuously long-length profiles. Materials under investigation are aluminum alloy EN AW 6063 and oxygen-free high-conductivity copper. The influences of substructural characteristic obtained by ECAP and ECAR technology on mechanical properties, as well as thermal and electrical conductivity, at operational cryogenic temperatures, at 77 K and 4.2 K, are observed.