V. S. Okovit

Structure parameters and degradation of the critical current of the alloy NT-50 after cryogenic drawing in an ultrasonic field

The parameters of the defect and phase structure of the alloy NT-50 are investigated after low-temperature (77 K) deformation by drawing in an ultrasonic field, and the influence of these parameters on the amount of degradation of the critical current under tensile loading at 4.2 K is studied. It is found that cryogenic ultrasonic deformation leads to intensified decomposition of the β-solid solution with precipitation of Ti-rich phases according to the kinetics of the spontaneous martensitic transformation and results in a reduction of the internal stress level in the alloys. The structural features found promote stabilization of the β-solid solution during a subsequent deep cooling, as is manifested in a lowering of the degree of completion of the low-temperature deformation-induced martensitic transformation, which in turn raises the threshold for degradation of the critical current and reduces the degree of degradation in a wide range of external mechanical loads.

About the nature of inelastic deformation of HTSC ceramics in region temperature below Tc

Abstract For Y- and Bi-based ceramics in superconducting state the results of the experimental studying the deformation under the loading are presented. The acoustic emission signals, the peculiarities of the intrinsic friction spectrum and ones of the planar contact resistance are studied. These results confirm the full analogy of the inelastic deformation processes at T c for HTSC ceramics and for metals.

Investigation of flux-trapping effect in Bi-based ceramics at 65–300 K

The influence of low magnetic fields on the temperature dependence of attenuation decrement is studied. The conservation of this effect after field switching off is discovered.

On the softening effect in superconducting state

It is shown that in superconducting state the increase of creep rate and peculiariries of attenuation decrement have dislocation origin.

Dependence of the shear modulus of a Bi ceramic on external influences in the temperature interval 65–130 K

The dynamic shear modulus of a two-phase bismuth ceramic (Bi-2212 and Bi-2223) is measured as a function of temperature, magnetic field, and deformation. The results attest to the multistage penetration of magnetic field into the sample. It is found that the level of the shear modulus is sensitive to the magnetic and defect structure of the ceramic. The conjecture that the observed defects of the shear modulus are due to phase separation in the CuO2 planes of the 2212 phase is discussed.