Roza G. Chembarisova

Analysis of the Deformation Behaviour of Cu Processed by High Pressure Torsion

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.

Dislocation–kinetic approach to the analysis of deformation mechanisms of metals and alloys

This paper presents the results of the development and application of a dislocation–kinetic approach to the analysis of strength and ductility in metals and alloys. The influence of the temperature–strain rate conditions of deformation on the character of dislocation processes, taking place in some pure metals and alloys, has been investigated here as well. Special attention has been given to the analysis of the effect of grain boundaries, twins, impurity atoms and a non–equilibrium state of the grain boundaries on the activation of one or another deformation mechanisms in bulk ultrafine–grained metallic materials, obtained by the severe plastic deformation method.

Kinetic Modeling of the Deformation Behavior of High-Strength Nanostructured Al-Mg Alloys

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.

Mechanisms of Deformation Behavior of Coarse-Grained and Ultrafine-Grained Ti

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.

The Analysis of SPD Paradox by Computer Modeling Technique

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.