Development of in-situ second phase pinning structure in niobium-titanium based superconducting alloys

A niobium-based superconducting alloy which has a rare-earth second phase that segregates between the matrix dendrites during solidification has been developed. The second phase can be refined by conventional deformation without heat treatment so as to form an in-situ fiber network. In such an alloy, one has independent control of the second-phase volume fraction as well as the matrix composition. The development of the in-situ alloy along with early microstructural and critical current results on the first wires are reported. The in-situ second phase was found to be about 2- mu m thick and 8- mu m apart in a conventionally solidified 35Nb-50Ti-15Y alloy. This size and spacing are suitable for producing a flux line lattice (FLL) pinning morphology in the strain available in conventional conductor processing. The properties of the test alloy are shown to be satisfactory with respect to easy melting, high ductility, and nondegraded superconducting properties.