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 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 метаданныеAnalysis of Mechanical Properties and Nanostructure Changes of VVER-440 Reactor Pressure Vessel Metal after Annealing(2021) Kryukov, A. M.; Chernobaeva, A. A.; Erak, D. Y.; Lebedinsky, V. I.; Rogozhkin, S. V.; Nikitin, A. A.; Рогожкин, Сергей Васильевич; Никитин, Александр Александрович© 2021, Pleiades Publishing, Ltd.Abstract: Analysis of mechanical testing and microstructural investigations of the irradiated VVER-440 reactor pressure vessel (RPV) metal before and after annealing carried out in the frameworks of the international project “PRIMAVERA” is presented. The role of chemical elements (Cu and P) was studied in relation to irradiation embrittlement of the VVER-440 RPV weld metal in the initial state, after recovery annealing and after post-annealing irradiation. It was shown that under primary irradiation, copper atoms formed small clusters (size ~1‒2 nm) which also include P, Si and Mn atoms. Phosphorus atoms also segregated on copper clusters, dislocations, grain boundaries, and additionally formed phosphorus clusters and atmospheres. Under thermal annealing at 475°C, the irradiation-induced copper-enriched and phosphorus clusters partially dissolved, increasing the copper concentration in the annealed metal, which was significantly lower compared to the unirradiated material. Since most copper atoms after annealing were not contained in the ferritic matrix but in precipitates, the contribution of copper atoms to an increase in the ductile-to-brittle transition temperature under re-irradiation was minimized and so hardening and embrittlement after subsequent post-annealing irradiation were lower than under primary irradiation.
- ПубликацияТолько метаданныеTEM analysis of radiation effects in ODS steels induced by swift heavy ions(2021) Vasiliev, A. L.; Presnyakov, M. Y.; Tomut, M.; Trautmann, C.; Rogozhkin, S. V.; Bogachev, A. А.; Nikitin, A. A.; Рогожкин, Сергей Васильевич; Богачев, Алексей Александрович; Никитин, Александр Александрович© 2020 Elsevier B.V.Oxide dispersion strengthened steels ODS Eurofer and ODS 13.5Cr-0.3Ti were irradiated with 945 MeV Au ions and 167 MeV Xe ions at room temperature. Beam-induced microstructural changes were analyzed by high-resolution transmission electron microscopy in the region of maximum electronic energy loss of 55 and 30 keV/nm, respectively. In both ODS steels, an increase in the fraction of small oxide inclusions (<5 nm) was observed. In ODS Eurofer steel, the irradiation with Xe and Au ions leads to the formation of amorphous tracks in yttrium oxide inclusions larger than 8 nm with track diameters of 2 nm and 3–4 nm, respectively.
- ПубликацияТолько метаданныеComprehensive Analysis of Nanostructure of Oxide Dispersion-Strengthened Steels by Ultramicroscopy Methods(2022) Rogozhkin, S. V.; Khomich, A. A.; Klauz, A. V.; Bogachev, A. А.; Nikitin, A. А.; Lukyanchuk, A. A.; Raznitsyn, O. A.; Shutov, A. S.; Zaluzhny, A. G.; Рогожкин, Сергей Васильевич; Клауз, Артём Вадимович; Богачев, Алексей Александрович; Никитин, Александр Александрович; Лукьянчук, Антон Алексеевич; Разницын, Олег Анатольевич; Шутов, Антон Сергеевич; Залужный, Александр ГеоргиевичAbstract: The characterization of the nanostructure of modern oxide dispersion strengthened steels requires a comprehensive analysis using complementary techniques. In this work, the methods of small-angle X-ray scattering, transmission electron microscopy and atom probe tomography have been applied to several oxide dispersion strengthened steels. Comparison of the obtained results allows the most correct characterization of inclusion types and their number in the studied materials. It is shown that most of the studied steels contain oxide inclusions and nanosized clusters enriched in O and Y, as well as V, Ti, Al, and Zr, depending on the initial steel composition. Transmission electron microscopy and atom probe tomography provide detailed information about the inclusion types, and small-angle X-ray scattering gives the most accurate estimation of the average density of inclusions in large volumes of material. The importance of the correct determination of the inclusion types for hardening calculations is shown, the results of such calculations are compared with microhardness measurements. The calculated values of hardness for the studied steels are in the range 2.7–4.3 GPa, which is well confirmed by microhardness measurements. © 2022, Pleiades Publishing, Ltd.
- ПубликацияТолько метаданныеStudy of Nanostructure of Oxide Dispersion-Strengthened Steels by Small-Angle X-Ray Scattering(2022) Rogozhkin, S. V.; Khomich, A. A.; Bogachev, A. А.; Nikitin, A. A.; Gorshkova, Yu. E.; Bokuchava, G. D.; Рогожкин, Сергей Васильевич; Богачев, Алексей Александрович; Никитин, Александр Александрович
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