The effect of multiple prolonged heat treatment on the structure and critical current density in Nb50 wt% Ti composites was studied in the case of monofilamentary superconductors. The treatment temperature range, in which high ic vaiues can be obiained, is aeierminea. i i n e iniiuence o i intermeaiaie ireaimenis on the increase in the quantity of precipitated a-phase is studied. The exponent specifying the kinetics of particle growth from the supersaturated solid solution is estimated. The interrelation between the critical current density and the quantity of precipitated phase is established. The maximum critical current density is 4 x IO5 A cm-' (E = 5 T).

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The effect of low temperature (77 K) deformation by drawing (80%) on the superconducting properties and structure of vanadium is studied. The structural elements (fragment boundaries) responsible for the observed changes of critical parameters are isolated. The electron-phonon coupling constant and the electron mean free path undergo most significant changes in these regions of rotational deformation localization, which have a high density of defects and are powerful sources of internal stresses. The dislocation density at the fragment boundaries is estimated.

For group-V transition metals (Nb, Ta) containing different concentrations of interstitial impurities (O, C, N, H) and deformation-induced defects, a numerical calculation of various effective microscopic characteristics averaged over the Fermi surface and of the band parameters in the framework of the Friedel model is carried out using the experimentally determined values of the superconducting transition temperature Tc and the temperature dependence of the resistivity in the interval Tc<T≲300 K. The causes of the polar character discerned in the influence of interstitial impurities and dislocations on the investigated physical characteristics are discussed.

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