Superconducting Properties of Niobium-Base Alloys

Abstract

Cast ternary Nb-Zr-Ti alloys are studied by x-ray diffraction after various forms of annealing and also in the quenched state. The ranges of existence of the various phases in isothermal cross sections of the ternary phase diagram are established. The decomposition of the solid solution in alloys situated within a wide area of the center of the concentration triangle takes place at temperatures below 600°, with the precipitation of the ß phase (bcc lattice) containing a large amount of niobium and the hexagonal aphase containing little niobium. The superconducting characteristics are measured for Nb-Zr-Ti and Nb-Ti alloys in the cast and worked states and also after the annealing of cast and worked samples. The rise in superconducting-transformation temperatures in cast alloys after annealing is explained by the precipitation of a new phase rich in niobium. The annealing of cast alloys has no effect on the critical magnetic field. Severe deformation only slightly increases this characteristic.