Персона: Никитин, Александр Александрович
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Институт ядерной физики и технологий
Цель ИЯФиТ и стратегия развития - создание и развитие научно-образовательного центра мирового уровня в области ядерной физики и технологий, радиационного материаловедения, физики элементарных частиц, астрофизики и космофизики.
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Александр Александрович
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- ПубликацияТолько метаданныеAtom Probe Tomography of the VV751P Nickel-Based Superalloy(2020) Ber, L. B.; Khomich, A. A.; Raznitsyn, O. A.; Lukyanchuk, A. A.; Rogozhkin, S. V.; Nikitin, A. A.; Zaluzhny, A. G.; Рогожкин, Сергей Васильевич; Никитин, Александр Александрович; Залужный, Александр Георгиевич© 2020, Pleiades Publishing, Ltd.Abstract: This work presents the results of the study of three different blanks used for the production of disks for gas-turbine engines made of a granular Ni-based superalloy. The blanks differed in the heat treatments performed and in the complexes of mechanical characteristics. The scanning electron microscopy of the studied materials showed that the size of the γ-matrix grains was 30–50 micrometers. In addition, particles of the γ and γ' phases with a size from 10 to 70 nm were revealed in the volumes of all blanks. The morphology of these particles has been studied. Within the particles of the γ' phase, homogeneously distributed equiaxed clusters of atoms of γ-forming elements were revealed with a size of 1–4 nm and flattened clusters of the same size and the same chemical composition aligned into chains. In the particles of both phases and in the transition layers between them, concentrations of the alloying components and impurities have been determined. In the studied volumes of the three different blanks of the disks, the volume fractions of the γ' phase were found to be 68 ± 1, 61 ± 2, and 62 ± 4%.
- ПубликацияТолько метаданныеCharacterization of nano-sized particles in 14%Cr oxide dispersion strengthened (ODS) steel using classical and frontier microscopy methods(2020) Templeman, Y.; Khomich, A.; Pinkas, M.; Meshi, L.; Rogozhkin, S.; Nikitin, A.; Рогожкин, Сергей Васильевич; Никитин, Александр Александрович© 2019 Elsevier Inc.Oxide dispersion strengthened (ODS) steels exhibit superior mechanical properties and irradiation resistance due to nano-sized oxides, highly dispersed in the metallic matrix. The mechanical properties are affected by the structure, composition, size and density of the nano-sized oxides. Despite numerous reports on the characterization of these oxides, ambiguity regarding their composition, crystallographic structure and orientation relationship with the matrix remains. In the present study, characterization of the crystallographic structure of oxide particles existing in 14%Cr ODS steel was performed using classical and novel transmission electron microscopy (TEM) methods. 3D dispersion, density and composition of these oxides were evaluated by atom probe tomography (APT). Three populations of particles were detected: highly dispersed, 3–20 nm Fe(Cr,Ti,Y)O particles with spinel structure; 50–150 nm YTiO3 and large (100–200 nm) particles identified as cubic TiC. The spinel-type particles displayed Bain and Kurdjumov-Sachs orientation relationships (OR) with the ferritic matrix. Applying electron diffraction tomography, the YTiO3 structure was attributed to the GdFeO3 (distorted perovskite)-type and its lattice parameters were refined as a = 5.46 Å, b = 7.66 Å and c = 5.28 Å. Orientation relationship of the YTiO3 particles and Fe matrix were determined as [110]Fe//[210]oxide and (110)Fe//(002)oxide.
- ПубликацияТолько метаданныеComprehensive Analysis of Nanostructure of Oxide Dispersion Strengthened Steels as Prospective Materials for Nuclear Reactors(2020) Khomich, A. A.; Lukyanchuk, A. A.; Raznitsyn, O. A.; Shutov, A. S.; Rogozhkin, S. V.; Bogachev, A. А.; Nikitin, A. A.; Рогожкин, Сергей Васильевич; Богачев, Алексей Александрович; Никитин, Александр Александрович© 2020, Pleiades Publishing, Ltd.Abstract: The enhanced mechanical properties of oxide dispersion-strengthened (ODS) steels are mainly due to the high density of homogeneously distributed oxide inclusions. It is well known that some alloying elements, such as Ti, V, and Al, play an important role in the formation of oxides/nanoclusters and influence the density and size of these inclusions. In this paper, a wide range of ODS steels containing different alloying elements were studied. The microstructural analysis was performed using transmission electron microscopy and atom probe tomography. Different types of inclusions were found in the steels: oxides of the Y–Ti–O or Y–Al–O types with sizes of ~2–15 nm, and nanoclusters (2–5 nm) enriched in Y, O, and Cr, as well as Ti, V, and Al, when these elements were present in the material. It was shown that oxides made the main contribution to the steel strengthening, while the cluster contribution was comparable with that of oxides only in Austenitic ODS and 14Cr ODS steels.
- ПубликацияТолько метаданныеIon Radiation Impact on Microstructure and Mechanical Properties of W-6Re Alloy at 500 degrees C(2020) Nikitin, A. А.; Bobyr, N. P.; Rogozhkin, S. V.; Fedin, P. A.; Никитин, Александр Александрович; Рогожкин, Сергей ВасильевичThe paper reports the results of the ion irradiation impact on a monocrystalline tungsten alloy, W-6Re. This material is considered for use in the design of fusion reactors. Irradiation was carried out in order to simulate radiation effects and analyze the radiation resistance of the fusion reactor material. Specimens were irradiated with 5.6 MeV Fe ions at 500 degrees C up to a maximum damage dose of 8 dpa. Microstructure of W-6Re was analyzed before and after irradiation. It is shown with transmission electron microscopy that the formation of structural defects, dislocation loops with sizes of 2-15 nm and a number density of 1.2 x 10(23) m(-3) occurs as a result of irradiation. Detailed analysis by atomic probe tomography microscope revealed the decomposition of the solid solution with the formation of nanoscale segregations enriched in rhenium by 18 at %. The radiation-induced hardening of the irradiated layer is determined by nanoindentation. The strength increment was 1.6 GPa.
- ПубликацияТолько метаданныеAtom Probe Tomography of High-Entropy Alloy AlCoCrFeNi(2020) Rogozhkin, S. V.; Shutov, A. S.; Khomich, A. A.; Nikitin, A. A.; Рогожкин, Сергей Васильевич; Никитин, Александр АлександровичIn this paper, the results of study of the AlCoCrFeNi high-entropy alloy by means of atom probe tomography are presented. Two phases were found, one enriched in Fe and Cr and the other enriched in Ni and Al. Owing to the complex surface morphology and spatial configuration of the phases, they were analyzed by various statistical methods. The Fe-Cr phase has a honeycomb structure that contains Co particles with the characteristic size of similar to 10 nm. The enrichment of the cell boundaries in Fe and Cr atoms reaches 50 at %. In turn, the Al-Ni phase is enriched in each of these elements up to 30 at % and contains nanoscale precipitates of Fe and Cr atoms. The volume density of these clusters is similar to 5 x 10(22) cm(-3).
- ПубликацияТолько метаданныеNanostructure Evolution of Oxide Dispersion Strengthened Steels under Fe Ion Irradiation at 350°C(2020) Khomich, A. A.; Khoroshilov, V. V.; Kulevoy, T. V.; Fedin, P. A.; Rogozhkin, S. V.; Bogachev, A. А.; Nikitin, A. A.; Zaluzhnyi, A. G.; Рогожкин, Сергей Васильевич; Богачев, Алексей Александрович; Никитин, Александр Александрович; Залужный, Александр Георгиевич© 2020, Pleiades Publishing, Ltd.Abstract: Improved mechanical properties of oxide dispersion strengthened (ODS) steels, the advanced materials for the reactor core, are due to the high density of uniformly distributed nanosized oxide inclusions. Transformation of the nanostructure of ODS steels under irradiation determines their stability during operation in the reactor conditions. In this work, three ODS steels are studied: Eurofer ODS, 10Cr ODS, and KP-3 ODS with different alloying systems. In these steels, the chromium content varies from 9 to 14 at %; such alloying elements as V, Ti, Al, W, and Mn are present in different proportions. The effect of irradiation with iron ions up to 3, 6, and 30 dpa at a temperature of 350°C was studied. The radiation-induced changes were analyzed by transmission electron microscopy and atom probe tomography. Although the sizes of oxide inclusions remained almost without change under irradiation, a decrease in their number density was observed in 10Cr ODS and KP-3 ODS steels, while the number density of oxides in Eurofer ODS steel did not change under the irradiation to 30 dpa. On the whole, the strengthening of the ODS steels due to inclusions during the irradiation to 30 dpa at 350°C changed insignificantly, which indicates their radiation resistance and their low propensity for low-temperature radiation strengthening and embrittlement.
- ПубликацияТолько метаданныеStudy of Silicon and the Transition Layer between Titanium and Titanium Oxide by Laser-Assisted Atom Probe Tomography(2020) Raznitsyna, I. A.; Raznitsyn, O. A.; Lukyanchuk, A. A.; Shutov, A. S.; Khomich, A. A.; Khoroshilov, V. V.; Nikitin, A. A.; Aleev, A. A.; Rogozhkin, S. V.; Разницын, Олег Анатольевич; Лукьянчук, Антон Алексеевич; Шутов, Антон Сергеевич; Никитин, Александр Александрович; Алеев, Андрей Аскольдович; Рогожкин, Сергей Васильевич© 2020, Pleiades Publishing, Ltd.Abstract: Monitoring the characteristics of nanoscale objects is a necessary step in the development of new materials and complex low-dimensional systems. Atom-probe tomography is among the few methods that allow one to study nanoscale objects with a complex chemical composition. However, preliminary optimization of the instrument parameters is necessary for each speciment to obtain the most accurate characteristics of the materials. In this study, the results of optimization of conditions for the analysis of silicon and the titanium–titanium-oxide transition layer on a APPLE-3D atom-probe tomograph with the purpose of refining the atom-probe-tomography technique for metal–semiconductor structures are presented. The optimal laser-pulse power for studying mixtures of these materials is determined. The atomic structure of the titanium–titanium-oxide interface layer is visualized, and the concentration profiles of evaporated Ti and TiOx ions in the transition layer are obtained.
- ПубликацияТолько метаданныеStudy of Microscopic Origins of Radiation Hardening of Eurofer 97 in Simulation Experiment with Ion Irradiation(2019) Khomich, A. A.; Iskandarov, N. A.; Khoroshilov, V. V.; Lukyanchuk, A. A.; Rogozhkin, S. V.; Nikitin, A. A.; Bogachev, A. A.; Рогожкин, Сергей Васильевич; Никитин, Александр Александрович; Богачев, Алексей Александрович© 2019, Pleiades Publishing, Ltd.Abstract: Low-temperature radiation hardening of prospective structural steel Eurofer 97 as the material for the first wall of the DEMO fusion reactor is studied in this work. Specimens of Eurofer 97 steel were irradiated with Fe ions up to 10 dpa at temperatures of 250, 300 and 400°C. Irradiated samples were studied by transmission electron microscopy and atom probe tomography. TEM study of irradiated samples showed preferential formation of dislocation loops at all temperatures of irradiation. Pair-correlation function analysis detected the initial stage of matrix solid solution decomposition of Eurofer 97 steel only at the temperature of 400°C. Detected microscopic changes and calculated hardening in the framework of the DBH (dispersed barrier hardening) model have shown that formation of dislocation loops is the main origin of low temperature radiation hardening of Eurofer 97 under irradiation with Fe ions with fluence up to 10 dpa.
- ПубликацияТолько метаданныеThe influence of Fe-ion irradiation on the microstructure of reduced activation ferritic-martensitic steel Eurofer 97(2019) Khomich, A. A.; Lukyanchuk, A. A.; Raznitsyn, O. A.; Shutov, A. S.; Rogozhkin, S. V.; Nikitin, A. A.; Рогожкин, Сергей Васильевич; Никитин, Александр АлександровичReduced activation ferritic/martensitic steels for in-vessel components of a fusion reactor have shown a decrease in plasticity and radiation hardening at low irradiation temperatures. The formation of dislocation loops and embryos of alpha' phase is considered the main reason for these effects. In this work, Eurofer 97 steel was irradiated with 5.6 MeV Fe2+ ions up to 10(20) m(-2) at 250, 300 and 400 degrees C. Transmission electron microscopy study of ion irradiated samples revealed nucleation of dislocation loops. The pair-correlation analysis of atom probe tomography data detected an initial stage of solid solution decomposition. The hardening of ion-irradiated Eurofer 97 was calculated with the dispersed barrier hardening model, taking into account radiation-induced dislocation loops to compare it with the change of yield stress in neutron-irradiated Eurofer 97. According to the obtained results, it can be supposed that the formation of dislocation loops plays the main role in the low-temperature radiation hardening of Eurofer 97 at a dose level up to similar to 10 dpa.
- ПубликацияТолько метаданныеA Study of the Effect of Ion Irradiation on the Mechanical Properties of Eurofer 97 Steel(2019) Gladkikh, E. V.; Kravchuk, K. S.; Useinov, A. S.; Nikitin, A. A.; Rogozhkin, S. V.; Никитин, Александр Александрович; Рогожкин, Сергей ВасильевичThe hardness values of samples of ferritic-martensitic steel Eurofer 97 in the initial state and after irradiation with 5.6 MeV Fe2+ ions up to a fluence of 1 x 10(16) cm(-2) at a temperature of 300 degrees C are compared. The mechanical properties are tested by the method of instrumental indentation using the dynamic mechanical analysis technique. To correct the obtained hardness values, the geometry of the plastic imprints is measured by the method of atomic force microscopy. Irradiation with heavy ions gives rise to an increase in the hardness value in comparison with the initial sample. This indicates a radiation-induced decrease in the plasticity of steel Eurofer 97, which should be taken into account in the case of using it as a construction material for new-generation fusion reactors.
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