Papers by Author: Yuriy Perlovich

Abstract: Texture and substructure changes in cladding tubes from Zr-based alloys under neutron irradiation in the atomic reactor during 6 years were investigated by use of X-ray methods. For this aim in the “hot” laboratory the automated X-ray diffractometer was set and the technique to handle with irradiated samples was elaborated. The residual radiation activity of samples correlates with integral texture Kearns parameters of tube, so that the texture weakens as the doze of neutron irradiation grows. Because of the initial substructure inhomogeneity of cladding tubes its changes under neutron irradiation are also inhomogeneous: relatively perfect grains of texture maxima become more distorted, whereas initially distorted grains of texture minima becomes more perfect.

Abstract: Based on the data of X-ray texture and structure analysis of the material of main gas pipelines it was shown that the layerwise inhomogeneity of tubes is formed during their manufacturing. The layerwise texture inhomogeneity of steel tubes, obtained by hot rolling at the air, differs depending on variation of technological parameters of their processing in inner and outer layers, i.e. the temperature and deformation gradients, penetration of interstitial impurities into the surface layer from surrounding atmosphere etc. The thickness of the surface layer with modified texture parameters depends on the temperature of rolling and its regime. Under exploitation when stress-corrosion cracks grows and reach the layer with a modified texture, their opening is slowing down or stops because of the high mutual misorientation of grains of different layers and the necessity of changing the plane of moving cracks, what requires additional tensile stresses. Layered textures of different gas tubes were compared. It was shown that character and degree of arising inhomogeneity correlates with the tubes resistance to stress-corrosion cracking.

Abstract: In this paper investigation results of behavior of promising superelastic alloys of Ti-Nb-Zr system in blood-vessel are presented. The possibility of their use in manufacturing of medical stents is examined. Based on analytical review of present scientific papers, four different alloys of Ti-Nb-Zr system are taken in consideration. A finite element modelling of stent behavior during delivery and opening stages is considered. These processes are done for two typical stent geometries and four alloys possessing different mechanical properties. Finite modelling results are analyzed to show the distribution of internal stresses, mechanical aspects of stent installation and effectiveness of various configurations to widen the narrowed vessel. Modeling has allowed to formulate recommendations for optimal mechanical characteristics of the superelastic alloy used for the manufacture of medical stents.

Abstract: The X-ray method of Generalized Pole Figures was used by study of residual deformation effects in steel shell tubes for high-temperature atomic reactor. Ferritic-martensitic steel contained disperse strengthening oxide particles and their behavior under technological treatment was of essential practical interest. The used procedure estimates residual deformation effects in grains with different orientations and depicts distributions of elastic lattice distortion and interplanar spacings. Invisible oxide particles redistribute within the tube wall and strain hardening at its outer side is higher.

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.

Abstract: Data are presented on the x-ray line broadening distribution over the texture of cold-rolled Nb and Mo sheets. The method of generalized X-ray pole figures, which combine texture measurements with X-ray line profile analysis, is employed. The X-ray line broadening is considered as an indicator of residual deformation effects. It was revealed that these effects in cold-rolled BCC metals rise as the grain orientation shifts away from texture maxima towards texture minima. The intensity of X-ray reflections change during annealing at 200 – 500C and this change correlates with the line broadening. The recrystallization texture of BCC metals is dominated by orientations deflected from the peak maxima by 25 – 30 deg. These orientations in the deformed structure have relatively high stored energy. Their volume fraction is sufficient for them to be able to consume most of the deformed matrix.

Abstract: Under rolling of Ti-48%Ni-2%Fe single crystals in the phase B2 at 350oC the twinning is the main mechanism of plastic deformation by many initial orientations of these single crystals, as texture data show clearly. Splitting of initial maxima in the stereographic projection of single crystal into several new ones is an evident manifestation of twinning. But this mode of reorientation is observed only at initial stages of rolling, when deformation degrees do not exceed ~10-15%. A geometrical analysis of pole figures for rolled single crystals showed, that at the used rolling temperature the preferable twinning planes there were {114} and {118}.

Abstract: Typical modes of the microstress distribution were found by X-ray study of Ti-Ni rolled single crystals using the X-ray method of Generalized Pole Figures. The method consists in successive measurements of the peak position 2θ for the same X-ray line of B2 phase by all possible positions of the sample in the course of diffractometric study of its texture. In the case of one-component rolling texture maxima in pole figure break into halves with opposite signs of elastic deformation, whereas by two-component rolling textures the one-sign elastic strain dominates within different maxima.

Abstract: The method was developed for quantitative estimation of inputs to plastic deformation of crystallographic and non-crystallographic modes of slip by data of X-ray texture measurements. The texture analysis allows to split material into fractions, deformed by predominant operation of crystallographic and non-crystallographic mechanisms, differing in final orientations of grains. Whereas texture maxima in pole figures correspond to grains, deformed by means of crystallographic slip and having predictable final orientations, texture minima are formed by grains, whose deformation does not submit to crystallographic regularities and therefore their orientations are deflected from stable positions or even prove to be arbitrary. These effects are demonstrated as applied to semi-products from Zr-based alloys, subjected to the deformation treatment at temperatures of the (α+β)-region of Zr-Nb phase diagram.

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.