Comparative characterization of Cu–Ni substrates for coated conductors

• Three Cu–Ni alloys were examined after heavy rolling and annealing.
• Fractions of the cube texture and HABs are sensitive to the chemical composition.
• For each alloy these fractions increase with increasing annealing temperature.
• The hardness of the substrates increases with increasing concentration of Ni.

Three Cu100−xNix alloys, with x = 23, 33 and 45 at.%Ni, have been evaluated for use as substrates for coated conductors on the basis of measurements of their microstructure, crystallographic texture and hardness. It is found that high-temperature annealing after heavy rolling generates strong cube textures in each investigated alloy. For all of these alloys an increase in the annealing temperature from 800 to 1000 °C strengthens the cube texture and reduces the fraction of high angle grain boundaries. In the Cu–23 at.%Ni and Cu–33 at.%Ni alloys annealed at 1000 °C for 1 h, the fraction of the cube texture approaches 100% and the fraction of high angle boundaries is less than 4%. These two alloys are however very soft in the annealed condition. The cube texture in the Cu–45 at.%Ni substrate is slightly weaker than in the two other alloys, but this substrate is considerably harder, which makes it better suited for large scale production of superconducting tapes.