Mechanical properties of pure Ni and Ni-alloy substrate materials for Y–Ba–Cu–O coated superconductors

Abstract Mechanical properties of rolling-assisted, biaxially-textured substrates (RABiTS) and substrates for ion-beam assisted deposition (IBAD) coated superconductors are measured at room temperature, 76, and 4 K. Yield strength, Young’s modulus, and the proportional limit of elasticity are determined, tabulated and compared. Results obtained are intended to serve as a database of mechanical properties of substrates having the same anneal state and texture as those incorporated in the general class of RE–Ba–Cu–O coated conductor composites (RE = rare earth). The RABiTS materials measured are pure Ni, Ni–13at.%Cr, Ni–3at.%W–2at.%Fe, Ni–10at.%Cr–2at.%W, and Ni–5at.%W. The IBAD substrate materials included Inconel 625 and Hastelloy C-276. The Ni alloys are substantially stronger and show higher strains at the proportional limit than those of pure Ni. Substrates fully coated with buffer layers, ≈1 μm of Y–Ba–Cu–O, and 3–5 μm of Ag have similar mechanical properties (at 76 K) as the substrate alone. Somewhat surprisingly, plating an additional 30–40 μm of Cu stabilizer onto high-yield-strength (690 MPa) Hastelloy coated conductors ∼100 μm thick, reduces the overall yield strength of the composite structure by only about 10–12% at 76 K and 12–14% at room temperature; this indicates that the Cu layer, despite its relatively soft nature, contributes significantly to the overall strength of even high-strength coated conductors.