Papers by Author: Roza G. Chembarisova

Abstract: The analysis of the strength characteristics and electrical conductivity of annealed Cu-1.0wt.%Cr-0.1wt%Zr alloy subjected to subsequent deformation under various conditions was carried out by analytical modeling methods. The contributions of the regions with nanotwins, as well as such defects of the crystal structure as vacancies, alloying atoms, dislocations, and particles of the secondary phase to the strength and electrical conductivity of the material were estimated.

Abstract: Basing on the kinetic modeling, the role of microstructure peculiarities in formation of a revealed experimentally high-strength state of the nanostructured Al 6061 (Mg 0.8…1.2, Si 0.4…0.8, Cu 0.15…0.40, Cr 0.15…0.35, Mn 0.15, Fe 0.7, Zn 0.25, Ti 0.15 wt. %) alloy was analyzed, Possible strengthening mechanisms of the alloy subjected to high pressure torsion at room temperature have been considered. It has been shown that the grain size and segregation of Si, Cu and Mg atoms from the solid solution in the grain boundaries area are the main factors that enhance the alloy strength. Conclusions on the deformation mechanisms acting in the considered alloy have been made. They can be helpful for predicting the mechanical properties of materials. Quantitative estimation of the dislocation density, the stress of dislocation strengthening, and the stress of dislocation pinning by Mg atoms has been made.

Abstract: A grain size is known to be one of the factors which define mechanical properties of metallic materials. At the same time the mechanisms which regulate the deformation behavior of bulk ultrafine-grained (UFG) metals produced by the severe plastic deformation method are still a subject for intensive study and fixed ambiguously. The report presents the developed model and the results of its application for kinetic modeling of the deformation behavior of coarse-grained (CG) and UFG Ti. Modeling has been carried out considering the possible contribution of dislocation slip and ageing. Conclusions about the role of the investigated mechanisms in the appearance of the peculiarities of the deformation behavior of CG and UFG Ti have been made.

Abstract: The paper has viewed the manifestation of the paradox of severe plastic deformation (SPD), caused by the occurrence of preexisting deformation twins in ultrafine-grained Cu, which has been obtained by the combination of the SPD method, accomplished by an equal-channel angular pressing with the conventional methods of deformation-thermal treatment. The high strength of the obtained samples has proved to be conditioned by the occurrence of the high density of the coherent twin boundaries, serving as effective obstacles on the way of slipping dislocations. Moreover, the occurrence of the twins creates favorable conditions for the dislocation density increase both in the grains with the twins and in the grains without them. As a result the sample hardens, contributing additionally into its strength. Simultaneously it manifests high ductility. By doing so the deformation behavior of the sample is mainly conditioned by the grain boundaries of grains free from the twins. The results were obtained on the basis of the dislocation-based model which develops models of Y. Estrin and L. Tóth, M. Zehetbauer, and L. Remy.

Abstract: In the investigation the 3D version of the Estrin-Tóth dislocation model was used to analyze deformation behaviour of pure Cu, subjected to high pressure torsion (HPT) under pressures equal to 0.8, 2, 5, 8 GPa. As a result of the computer simulation, the nature and reasons for strain hardening are analyzed, the dislocation density evolution versus degree of SPD and graincell size versus degree of SPD curves were plotted. It is shown that the model adequately reflects the acting deformation mechanisms and structural changes during HPT at different applied pressures. It has been stated that an increase of the applied pressure at HPT leads to an increase in the activity of dislocation sources and sinks in the grain-cell walls. Misorientations between boundaries are estimated. It is revealed that an increase of the applied pressure contributes to a growth of the misorientation angles between neighbouring grain-cells.