Dmitry V. Lychagin

The Effect of a Severe Plastic Deformation by Groove Pressing on the Grain Structure of the Al-Mg Alloy

In this article, the effect of a severe plastic deformation (SPD) achieved by groove pressing (GP) on the grain structure and mechanical properties of a rolled sheet Al-Mg alloy was investigated. The study of the microstructure of the samples before and after processing was carried out by means of electron backscattered diffraction (EBSD). The mechanical properties of the samples were experimentally studied under uniaxial tension in quasi-static conditions, and microhardness testing was implemented. It was found that the conventional yield strength and ultimate tensile strength increase by the factor of 1.4 and 1.5, respectively; and the microhardness increases by approximately 2.7 times after four machining sequences of the rolled sheet alloy. A bimodal grain structure, consisting of two grain types with particular features, is formed in the samples after four machining sequences of GP.

Laws of Development of Deformation Folds in [1- 11] Copper Single Crystal at Axis Compression

. Deformation folds on the surface of copper single crystal with compression axis orientation [] are analysed. Folds are an element of the deformation relief on meso-and macro-level secondary to macrobands. Folds are generated in several major crystal areas due to sample bending or striation in its end area.

Characteristic Features of Physical and Mechanical Properties of Ultrafine-Grained Al–Mg Alloy 1560

Specimens of Al–Mg alloy 1560 of ultrafine-grained structure were obtained by the method of severe plastic deformation based on multiple equal-channel angular pressing. Impact on physical and mechanical properties of the processed material and fracture pattern of specimens was studied. Tensile tests showed an increase of the offset yield strength and resistance to rupture with decrease in the ultimate deformation. The obtained specimens have increased microhardness values compared to the initial ones. It was established that the last cycle of pressing determines the structural orientation of macroscopic shear bands occurring at an angle to the specimen longitudinal axis while passing connection of channels. It affects the physical and mechanical properties of the material and fracture pattern. The quality control of the obtained specimens by the method of ultrasonic defectoscopy and X-ray tomography confirmed the absence of macroand microdefects when following the matched optimal regime of processing.

Compression strain-induced folding at intersecting deformation macrobands on the copper single crystals

Compression strain-induced surface pattern on copper single crystal faces was studied by means of optical, confocal laser and scanning electron microscopies. It was shown that apart from work-hardening effect of previously formed deformation macrobands there is a pure geometrical (size) effect which serves for changing the conditions for further deformation within the deformation macroband zones by folded structure formation.

Preferred Orientation Evolution of Olivine Grains as an Indicator of Change in the Deformation Mechanism

The paper presents the results of investigations of deformed natural polycrystalline olivine. The relationship of the structure of polycrystalline olivine grains to three modal size distributions has been revealed. Grains of different size were observed to be strained at threshold temperatures of 950, 775, and 650?C. It has been demonstrated that the microstructure develops as the dislocation mechanism changes from diffusion creep to grain boundary sliding. The changes in deformation mechanisms promote the change in the preferred crystallographic orientations of olivine from type A to type D and then to type B. The relation of the transitions between different types of orientations to the conditions of deformation in the lower layers of the lithosphere at the plate boundaries is discussed.

Folding on the lateral sides of copper monocrystals loaded by uniaxial compression and friction

Методами растровой и оптической микроскопии исследованы деформационные складки, сформированные на поверхности боковых граней монокристаллов при различных способах испытания. Обнаружено, что формирование складок различного структурно-масштабного уровня происходит по схожим причинам, связанным в основном с искривлением поверхностного слоя грани при образовании наплыва в приторцевой области. При сжатии складки формируются также в областях изгиба на боковых гранях и в местах стыка деформационных доменов.