Technique for developing highly strengthened and biaxially textured composite substrates for coated superconductor tapes

The development of reinforced and biaxially textured Ni5W/Ni9W/Ni5W composite substrate for coated conductor applications is presented. The configuration of this substrate is a thin, sharp cubic textured Ni5W outer layer on a Ni9W alloy core that provides the mechanical strength while decreasing the magnetization of the whole substrate. The key technique is to use thin Ag and Cu foils between initial Ni5W and Ni9W alloy pieces to bond them together, followed by cold-rolling and recrystallization. The obtained composite substrate has a very sharp cubic texture on the Ni5W outer layer and its yield strength approaches 200 MPa, thus being 50 MPa higher than commercially used Ni5W substrates. The saturation magnetization of this composite substrate at 77 K was reduced by 75% and 40% compared with pure Ni and Ni5W substrates, respectively. The present results show that this new substrate is suitable for the epitaxial growth of the CeO2 buffer layers.