Superconductivity of heat-treated Nb-65 at.% Ti alloy

Brief reviews are given of the effect of heat-treatment on the microstructure of cold-worked bcc metals and the superconducting properties of niobium alloys. Particular attention is paid to the influence of interstitial impurities in these processes. The annealing effects in microstructure and superconducting properties of a cold-worked Nb-65 at.% Ti alloy, containing oxygen as a major impurity, have been studied. The precipitation process takes the form TiNb + O₂ various Ti oxides Ti + TiO. Differences in precipitation sequence are described for vacuum-annealing and annealing in impure argon. Flux-pinning is related to the microstructural observations. At least three pinning mechanisms appear to operate; dislocation pinning and two types of precipitate pinning. These observations are in accord with previously proposed pinning models.