Papers by Author: Rinat K. Islamgaliev

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Authors: Rinat K. Islamgaliev, Marina A. Nikitina, Aidar F. Kamalov
Abstract: The paper reports on microstructure, strength and fatigue of ultrafine-grained (UFG) samples of the Al-Cu-Mg-Si aluminum alloy processed by high pressure torsion (HPT) at various temperatures. Application of the HPT treatment led to strong grain refinement, as well as to a raise of the mean-root square strains and dynamic precipitation. In case of optimal HPT treatment the UFG samples have demonstrated the enhanced thermal stability, an increase in ultimate tensile strength in 2.5 times and enhancement in fatigue endurance limit by 20 % in comparison with coarse-grained alloy subjected to standard treatment. It is shown that the regime of the HPT treatment governs the volume fraction of precipitates and segregations, thereby affecting a grain size and thermal stability of ultrafine-grained structure.
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Authors: L.K. Fionova, L.E. Polyak, Rinat K. Islamgaliev, Ruslan Valiev, V. Gueorguiev, R. Paneva, L. Popova
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Authors: Ruslan Valiev, Rinat K. Islamgaliev, N.F. Yunusova
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Authors: Yannick Champion, Jean Philippe Couzine, S. Tusseau Nenez, Yves Bréchet, Rinat K. Islamgaliev, Ruslan Valiev
Abstract: Copper based materials are still the most attractive low resistivity materials for microelectronics and electrotechnics applications, though, all variants developed to combine strength and conductivity, such as solid solutions and composites, suffer from decay in electric conductivity while strength is increased . In a addition, linear decay was also conjectured for pure copper when grain size is refined below the UFG and nanostructured domains (except when grain boundaries are pure twins). Copper alloys with low content of silver and chromium were prepared by high pressure torsion (HPT) with various annealing conditions. Vickers hardness and electric resistivity in the temperature range of 4K-340K, were measured as well as microstructural characterizations were performed using quantitative X-ray diffraction. Depending on the annealing conditions the alloys exhibit from 25% to 75% of IACS electric conductivity at room temperature and hardness in the range of 200 Hv. Origins of both high strength and high electric conductivity were investigated from microstructures analysis, using transmission electron microscopy and mechanical testing.
755
Authors: Oksana Melikhova, Jakub Čížek, Petr Hruška, Marián Vlček, Ivan Procházka, Martin Vlach, Ivana Stulíková, Bohumil Smola, Naďa Žaludová, Rinat K. Islamgaliev
Abstract: Precipitation effects in age-hardenable Mg-13wt.%Tb alloy were investigated in this work. The solution treated alloy was subjected to isochronal annealing and decomposition of the supersaturated solid solution was investigated by positron annihilation spectroscopy combined with transmission electron microscopy, electrical resistometry, differential scanning calorimetry and microhardness measurements. Peak hardening was observed at 200°C due to precipitation of finely dispersed particles of β phase with the D019 structure. Vacancy-like defects associated with β phase particles were detected by positron annihilation. At higher temperatures precipitation of β and subsequently β phase takes place. Formation of these phases lead to some additional hardening and introduces open volume defects at precipitate/matrix interfaces. To elucidate the effect of plastic deformation on the precipitation sequence we studied also a Mg-13wt.%Tb alloy with ultra fine grained structure prepared by high pressure torsion. In the ultra fine grained alloy precipitation of the β phase occurs at lower temperature compared to the coarse grained material and the peak hardening is shifted to a lower temperature as well. This effect can be explained by enhanced diffusivity of Mg and Tb atoms due to a dense network of grain boundaries and high density of dislocations introduced by severe plastic deformation. Moreover, dislocations and grain boundaries serve also as nucleation sites for precipitates. Hence, precipitation effects are accelerated in the alloy subjected to severe plastic deformation.
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Authors: Jakub Čížek, Ivan Procházka, Gerhard Brauer, W. Anwand, Radomír Kužel, Miroslav Cieslar, Rinat K. Islamgaliev
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Authors: Ruslan Valiev, Rinat K. Islamgaliev, N.F. Yunusova
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Authors: G.V. Nurislamova, Rinat K. Islamgaliev, Ruslan Valiev
Abstract: Microstructure and mechanical properties of pure nickel processed by high pressure torsion (HPT) and equal channel angular pressing (ECAP) have been investigated in the present paper. The uniformity of microstructure and misorientation angles in the SPD samples were studied using transmission electron microscopy and electron back scattering diffraction. Microstructural requirements for achivement of high strength and ductility in SPD metals are discussed.
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Authors: Jakub Čížek, Ivan Procházka, Bohumil Smola, Ivana Stulíková, Radomír Kužel, Z. Matěj, V. Cherkaska, Olya B. Kulyasova, Rinat K. Islamgaliev
Abstract: Bulk samples of pure Mg and Mg-Gd alloys were prepared by high-pressure torsion (HPT). The HPT made samples exhibit ultra fine grained (UFG) structure with grain size around 100 nm. Results of microstructure investigations of the UFG samples obtained by positron lifetime (PL) spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD) are presented. In particular, lattice defects introduced by HPT were characterized. The data obtained at atomistic level are compared with macroscopic properties given by microhardness measurements.
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