The strengthening mechanism of the metallic material is related to the hindrance of the dislocation motion, and it is possible to achieve superior strength by maximizing these obstacles. In this study, the multiple strengthening mechanism-based nanostructured steel with high density of defects was fabricated using high-pressure torsion at room and elevated temperatures. By combining multiple strengthening mechanisms, we enhanced the strength of Fe-15 Mn-0.6C-1.5 Al steel to 2.6 GPa. We have found that solute segregation at grain boundaries achieves nanograined and nanotwinned structures with higher strength than the segregation-free counterparts. The importance of the use of multiple deformation mechanism suggests the development of a wide range of strong nanotwinned and nanostructured materials via severe plastic deformation process.

The paper presents the results of a study on the microstructure and mechanical properties of a mediumcarbon steel (0.45 % C) processed by severe plastic deformation (SPD) via high-pressure torsion (HPT). Martensite quenching was first applied to the material, and then HPT processing was conducted at a temperature of 350°C. As a result, a nanocomposite type microstructure is formed: an ultrafine-grained (UFG) ferrite matrix with fine cementite particles located predominantly at the boundaries of ferrite grains. The processed steel is characterized by a high-strength state, with an ultimate tensile strength over 2500 MPa. Special attention is given to analysis of the thermal stability of the microstructure and properties of the steel after HPT processing in comparison with quenching. It is shown that the thermal stability of the UFG structure produced by HPT is visibly higher than that of quenchinginduced martensite. The origin of the enhanced strength and thermal stability of the UFG steel is discussed.

Enhancement in the strength of austenitic steels with a small content of carbon can be achieved by a limited number of methods, among which is ultrafine-grained (UFG) structure formation. This method is especially efficient with the use of severe plastic deformation (SPD) processing, which significantly increases the contribution of grain-boundary strengthening, and also involves a combination of the other strengthening factors (work hardening, twins, etc.). In this paper, we demonstrate that the use of SPD processing combined with conventional methods of deformation treatment of metals, such as rolling, may lead to additional strengthening of UFG steel.In the presented paper we analyze the microstructure and mechanical properties of the Cr-Ni stainless austenitic steel after a combined deformation. We report on substantial increases in the strength properties of this steel, resulting from a consecutive application of SPD processing via equal-channel angular pressing and rolling at a temperature of 400 • C. This combined loading yields a strength more than 1.5 times higher than those produced by either of these two techniques used separately.

The linear friction welding process of α+β titanium alloys VT6 and VT8M-1 has been studied and in particular the investigation of microstructure in the weld zone. The results of this investigation were used for development of a numerical model of LFW equilibrium stage using the ANSYS Mechanical software. The set of parameters used in this model allowed to reach a quantitative agreement with experiments

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