Effect of manganese additions of the physical and superconducting properties of Nb-46.5Ti

This paper reports a study of some physical- and superconductive properties of Nb-46.5Ti doped with (nominally) 2, 4, and 6 wt. % Mn. Properties measured were:residual resistivity, magnetic susceptibility, low- temperature specific heat (which yields the transition temperature, Tc, the Debye temperature, and the electronic specific heat coefficient), and (in the case of Cu-clad monofilamentary strands) upper critical field and critical current density, Jc. The beta-stabilizing strength of Mn, estimated from metallurgical data, is six times greater (on a weight basis) than that of Nb. Superconductive-property evidence places it as an even stronger beta stabilizer. As a result of the tendency of Mn to suppress the precipitation of alpha phase, the Jc of commercially processed Cu-clad Nb-46.5Ti-base monofilamentary strands decreases rapidly with Mn content to such and extent that Nb-46.5Ti-6Mn exhibits a peak effect