Microstructural evolution of nickel under high-pressure torsion

The evolution peculiarities of grain and defect structures in nickel under high-pressure torsion were studied by transmission electron microscopy and X-ray diffraction analysis. Lattice reorientation mechanisms characteristic of different stages of plastic deformation were disclosed. The conditions and features of cooperative realization of various structure formation mechanisms under severe deformation were discussed.     

Fraction of cosmic-ray positrons in the galaxy: Results from using the fractional diffusion approach

The fraction of positrons in the electron-positron component of cosmic rays is calculated in a scenario where electrons and positrons are generated by Galactic sources with the same spectral index. It is shown that the proposed scenario allows us to reproduce the existing experimental data on the fraction of positrons if the relative yield of positrons in a source is e ⁺/e ^? ≈ 0.3.     

Noncommutative Integration of the Dirac Equation in a Flat Space and in the de Sitter Space

Noncommutative integration of the Dirac massive and massless equations is performed in a four-dimensional flat space and in the de Sitter space of arbitrary signature. A new class of rigorous solutions of the Dirac equation is constructed in these spaces. The properties of the solutions obtained are examined.     

Structure–phase transformations and physical properties of ferritic–martensitic 12% chromium steels EK-181 and ChS-139

The thermophysical properties (specific heat, thermal diffusivity, thermal conductivity, linear thermal expansion coefficient, density) of 12% chromium ferritic–martensitic steels EK-181 (RUSFER-EK-181) and ChS-139 and the structure–phase transformations that occur in them upon heating and cooling in the temperature range 20–1100°C are studied. The temperatures of the start and finish of the α → γ and γ → α transformations in these steels and the Curie temperature are determined by differential scanning calorimetry. Peaks in the temperature dependence of the specific heat and jumplike changes in the linear thermal expansion coefficient and the density and the minimum of thermal diffusivity are detected in the α → γ transformation range. Specific heat peaks, thermal conductivity minima, and inflection points in thermal diffusivity curves are also observed near the Curie temperature.     

Substructure formation in high-strength dispersely strengthened alloys

Conclusions Analysis of new experimental laws of plastic flow observed in high-strength alloys with dispersional strengthening (such as the formation of substructure with high crystal-lattice curvature, high-temperature localization of deformation from the earliest stages, with reorientation of the localized-shear zones and the adjacent undeformed structural elements) leads to the conclusion that deformational point defects play an important role in the realization of collective deformational modes in the high-strength state.In conditions of high nonequilibrium concentration, deformational point defects, first, permit the inclusion of quasi-viscous diffusional mechanisms of crystal-lattice reorientation by point-defect drift in the local fields of high inhomogeneous stress and, second, by facilitating dislocational deformation mechanisms, may lead to local weakening of the shear zones, localization of the plastic flow, and stability loss, in particular, as a result of mutually consistent autocatalytic defect multiplication.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 81–92, March, 1991.     

Manifestation of the Effect of Self-Activation in Formation of Carbon Fiber Structure in High-Temperature Treatment

X-ray structural analysis was applied to study recrystallization of the material of carbon fiber in high-speed high-temperature (up to 3200°C) thermomechanical treatment. The time of heating of a fiber bundle is evaluated.     

Amorphization of metals by ion implantation and ion mixing methods

In this paper, we present a review of the experimentally determined characteristics of solid-phase amorphization of metals and alloys under ion implantation and ion mixing conditions. For the first time we systematically consider the characteristic features and the thermodynamic, structural, and kinetic criteria for amorphization in different metallic systems, and we demonstrate the expediency of the following classification of alloys undergoing amorphization: metal-metalloid systems, intermetallics, heterophase alloys, alloys with high positive heat of mixing. We compare solid-phase amorphization under conditions of bombardment by beams of charged particles, thermal mixing of the alloy components, and mechanical alloying. We consider the phase and structural states preceding amorphization and the possibilities for predicting metallic systems which can undergo amorphization.V. D. Kuznets Siberian Physicotechnical Institute, Tomsk University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 3–30, August, 1994.     

Mechanisms of deformation localization and mechanical twinning under the conditions of phase instability of a crystal in stress fields

A new mechanism of the deformation and reorientation of a crystal has been studied experimentally and theoretically. This mechanism, which is effective in strain localization mechanical twinning bands of metal alloys and intermetallides, is a mechanism of dynamic phase (direct plus reverse martensitic) transformations in fields of high local stresses. The features of the reorientation and the defect substructure in these bands are discussed using electron microscopy data. With models of martensitic transformations based on the concept of cooperative thermal vibrations of extended coherent objects in crystals, the atomic mechanisms of direct plus reverse transformations are analyzed and the reorientation matrices (vectors) and distortion tensors are calculated for some (fcc bcc fcc, bcc hcp bcc) variants of these transformations. The carriers and nature of the above deformation mechanism and the principal physical effects underlying this mechanism are discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 28–48, August, 2004.     

Discontinuous decomposition in quenched and deformed alloys

Discontinuous decomposition in quenched and deformed samples of the alloy Cu + 4.3% Ti has been studied by optical metallography and by electron metallography (with replicas and thin foils). The structure of the discontinuous-decomposition regions changes markedly during the continuous metastable decomposition in the matrix. Cells are nucleated within grains in the deformed samples at recrystallization nuclei.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 1, pp. 108–112, January, 1969.