Papers by Author: Olga Krymskaya

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Authors: Margarita Isaenkova, Yuriy Perlovich, Vladimir Fesenko, Olga Krymskaya
Abstract: Possibilities of X-ray methods, using diffractometric measurements of X-ray line profiles and crystallographic texture, are compared as applied to study of SPD metal materials. The texture analysis gives the most direct data on the degree of grain fragmentation under conditions of deformation. The consideration is illustrated by results, obtained by X-ray studies of ECAP rods from Cu and Ti.
Authors: Olga Krymskaya, Margarita Isaenkova, Yuriy Perlovich
Abstract: The method for grain size determination by statistical fluctuations of X-ray intensity, registered during measurement of texture pole figures, was developed. Niobium and bronze rods as well as tubes from Zr-1%Nb alloy, subjected to annealing at different temperatures, were studied. Description of the method, pole figures (PF), X-ray intensity distribution within PF circular sections, grain size values and their errors are presented.
Authors: Margarita Isaenkova, Yuriy Perlovich, Vladimir Fesenko, Olga Krymskaya, Alexander Zavodchikov
Abstract: The deformation behavior of commercial Zr alloys with 1% and 2,5%Nb under compression at temperatures of the (α+β)-region of Zr-Nb phase diagram is considered on the basis of experimental data obtained by X-ray texture study of deformed samples. Mechanisms, responsible for plastic deformation of alloys by different temperature-rate regimes were determined on the basis of resulting textures. Among these mechanisms there are crystallographic slip and mutual displacements of crystallites along interphase boundaries. The latter mechanism sharply intensifies by grain fragmentation down to nanostructuring under conditions of α«β phase transformations. Texture features of deformed samples testify about interaction of plastic deformation with phase transformations and indicate that due to this interaction compression by optimal regimes promotes the utmost refinement of structure elements.
Authors: Yuriy Perlovich, Margarita Isaenkova, M. Grekhov, Olga Krymskaya, Vladimir Fesenko, S. Zavodchikov, V. Kotrekhov
Abstract: Distinctive structure features of rods produced by hot and cold radial forging of a Zr- 2.5%Nb alloy were revealed. Most experimental data were obtained by X-ray methods. Among considered aspects, connected with the undulatory mechanism of energy transfer, there are the uniformity of bulk deformation, structure perfection under hot radial forging, the demolition of secondary phases and the oversaturation of α-Zr with Nb under cold radial forging, the role of phase transformations in deformation, and the suppression of recrystallization by annealing. Structure, texture and properties of products, produced by radial forging from Zr-based alloys, allow to consider this technology as an acceptable alternative to that usable nowadays.
Authors: Margarita Isaenkova, Yury Perlovich, Pavel Medvedev, Olga Krymskaya, Soe San Thu
Abstract: Shell tubes from Zr-based alloys are responsible construction elements of atomic reactors. Under exploitation these tubes undergo to oxidation, which can become a reason for their cracking. Inevitable texture layering arises by rolling of tubes due to different values of the Q-factor, calculated for inside and outside tube layers. Therefore these layers are characterized by different texture Kearns parameters and, correspondingly, by different thermal expansion. As a result, tensile tangential macrostress operates between layers and oxygen diffusion into tube intensifies.
Authors: Margarita Isaenkova, Yuriy Perlovich, Nikolay Krapivka, Vladimir Fesenko, Olga Krymskaya, Alina Sudakova
Abstract: Recrystallization of rolled Zr single crystals is considered in comparison with analogous recrystallization processes in rolled coarse-grained iodide Zr and polycrystalline plates of commercially pure Zr. Diffractometric X-ray methods were used by texture and X-ray line profile measurements. The treatment of obtained data included construction of correlation diagrams, connecting as-rolled and recrystallized conditions of samples. A number of recrystallization mechanisms, operating in rolled α-Zr under annealing, were revealed on the basis of found regularities of texture changes.
Authors: Margarita Isaenkova, Yuriy Perlovich, Vladimir Fesenko, Sergey Kropachev, Olga Krymskaya
Abstract: Deformation behavior of Zr-based alloys by forging under conditions of α↔β phase transformations was considered as applied to model samples and real semi-products. Model samples were deformed by uniaxial compression at temperatures of β- and (α+β)-regions of the phase diagram Zr-Nb. Mechanisms, responsible for plastic deformation of alloys by different temperature-rate regimes, were determined on the basis of textures, arising in deformed samples. Among these mechanisms there are crystallographic slip in grains of β-Zr and α-Zr as well as mutual displace¬ments of crystallites along interphase boundaries. The latter mechanism sharply intensifies under conditions of α«β phase transformations and lies in the basis of superplasticity. An input of each mechanism into plastic deformation of material depends on the temperature-rate regime of compression and determines its anisotropy.
Authors: Yuriy Perlovich, Margarita Isaenkova, Vladimir Fesenko, Olga Krymskaya
Abstract: Abstract. Features of the texture development in Zr-based alloys under compression at tempera-tures of the (α+β)-region of the Zr-Nb phase diagram indicate that the plastic deformation shifts temperatures of phase transformations due to accompanying thermal effects and the decrease of lattice stability, whereas formation of the fine-grained structure by phase transformation promotes activation of the non-crystallographic deformation mechanism of slip by interphase boundaries.
Authors: Yuriy Perlovich, Margarita Isaenkova, Vladimir Fesenko, Olga Krymskaya, Mikhail Lenskiy, Alexander Zavodchikov
Abstract: Features of the deformation process by cold radial forging of tube billets from Zr-1%Nb alloy were reconstructed on the basis of X-ray texture data. The cold radial forging intensifies grain fragmentation in the bulk of billet and increases significantly the latent hardening of potentially active slip systems, so that operation only of the single slip system becomes possible. As a result, in radially-forged billets unusual deformation and recrystallization textures arise, differing from usual textures of a-Zr by the mutual inversion of crystallographic axes, aligned along the axis of tube.
Authors: Yury Perlovich, Margarita Isaenkova, Olga Krymskaya, Vitaliy Baranov, Mikhail Perlovich, Andrey Tenishev
Abstract: Manufacture of fuel tablets from UO2 powder includes many processes, among which shrinkage without application of external loading till now requires explanations. Particles of UO2 are brittle up to ~ 700°C. By cold pressing due to the porous structure of powder billets separate particles are pressing one into another with accompanying rise of residual elastic stress. Under following heating and sintering plasticization of UO2 occurs, its yield stress decreases and conditions for creep and resulting shrinkage of tablets takes place.
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