A. A. Aleev

Institute for Theoretical and Experimental Physics, Moskva, Moscow, Russia

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Publications (14)9.32 Total impact

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    ABSTRACT: It is shown that simulation experiments on the heavy-ion irradiation of structural materials used in nuclear power facilities can be used for tomographic atomic-stand studies. Experiments have been performed on irradiation of samples of advanced steel used in nuclear and fusion reactors EK-181 and ODS Eurofer by iron ions to damaging dose 10 dpa. The steel is characterized by the presence of a large number of nanosize (2–3 nm) clusters, dispersion-hardening these materials. Irradiation was performed on the TIPr-1 heavyion linear accelerator. Atomic-probe studies of irradiated samples reveal a change in the composition of nanosize clusters under irradiation.
    Atomic Energy 05/2013; 114(1). · 0.03 Impact Factor
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    ABSTRACT: The influence of Fe ion irradiation up to a dose of 10 dpa on the distribution of chemical elements and on the fine structure of advanced steel Rusfer EK-181 was studied by tomographic atom probe. The processes of element redistribution and changes in element composition, size, and number density of detected clusters were shown to occur. The increase in cluster size under irradiation was accompanied by the decrease in vanadium, chromium, and nitrogen concentrations in the clusters.
    Inorganic Materials: Applied Research. 01/2013; 4(5).
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    ABSTRACT: The analysis of WWER-440 RPV welds mechanical properties and behaviour of nanoscale structural features under primary irradiation, thermal annealing and re-irradiation has been performed in the framework of the international research project PRIMAVERA. The weld material of WWER-440 with three different levels of phosphorus contents, specifically 0.025, 0.03 and 0.04 wt.% were investigated in the framework of the project.It has been demonstrated that the copper atoms create under irradiation small clusters (d ∼ 1–2 nm) surrounded by P, Si or Mn atoms. The phosphorus atoms segregate on Cu-clusters, dislocations and form P-clusters and atmospheres. These mechanisms lead to the embrittlement of RPV steel, which is revealed by the increasing of yield stress and transition temperature shift after irradiation.Due to thermal annealing a substantial part of irradiation induced copper and phosphorus clusters has been dissolved. Moreover, dissolution of Cu clusters occurs simultaneously with the growth of the Cu precipitates. Both steel tensile properties and transition temperature recover due to thermal annealing.A substantial phosphorus effect on ductile-to-brittle transition temperature shift occurs under re-irradiation. Because in the annealed steel a substantial part of the Cu atoms is in the precipitates, the material embrittlement under re-irradiation does not depend so much on Cu, and the Tk shift under re-irradiation is less as compared with primary irradiation.Considering the vacancy type defects, the PAS experiments show that basically three different processes play a role in the microstructure evolution: irradiation induced creation of point defects, thermal induced annealing of these defects and thermal/irradiation induced coarsening of defects. Although, the influence of the vacancy type defects on the mechanical properties was found to be little in comparison to the effect of the Cu–P clusters, the presence of these defects in the irradiated and annealed materials were observed in large number-significantly more than in an equilibrium state.
    Journal of Nuclear Materials 10/2012; 429(s 1–3):190–200. · 2.02 Impact Factor
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    ABSTRACT: An imitation experimental technique on the irradiation with heavy ions of structural materials of nuclear power plants using tomographic atom probe analysis has been elaborated. The scheme of irradiation of specimens for atom probe analysis has been realized on a MEVVA ion source of an TIPr accelerator (ITEP) with ion energy 75 keV per charge. Test experiments with irradiation and analysis of samples of the EK-181 steel by aluminum ions to a fluence of ∼2 × 1015 ion/cm2 have been performed. Experiments on the Fe-ion irradiation of the samples of ODS EUROFER perspective steel for fission and fusion reactors to different damaging doses have been carried out. The analysis of distribution of different chemical elements in the volumes tested has revealed that under ion irradiation a change in the composition of nanosized clusters, which are present in the initial material takes place. Comparison of the data obtained with the results of reactor irradiation of the ODS EUROFER steel has been carried out. These data testify a correspondence between nanoscale changes in the steels oxide dispersion strengthened in imitation experiments and under the conditions of reactor irradiation.
    The Physics of Metals and Metallography 02/2012; 113(2). · 0.57 Impact Factor
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    ABSTRACT: Atom probe tomography has been used to investigate nanoscale features in the yttrium oxide dispersion strengthened steel ODS Eurofer, which is a perspective structural material for the reactor cores. In the initial material, a large number (similar to 2 x 10(24) m(-3)) of ultrafine (similar to 2.5 nm in diameter) clusters enriched in yttrium, oxygen, nitrogen, and vanadium have been revealed. The investigation of the ODS Eurofer steel irradiated at 330A degrees C to 32 dpa in the BOR-60 fast reactor has also revealed a large number of ultrafine (1-3 nm in diameter) nanoclusters significantly enriched in yttrium, oxygen, manganese, and chromium. In the irradiated material, an increase in the concentration of clusters and changes in the chemical composition of the clusters and matrix have been noted. The irradiation by fast neutrons leads to a partial transition of vanadium from the clusters into the surrounding matrix and to a general increase in the concentrations of yttrium and oxygen in the volumes under investigation.
    The Physics of Metals and Metallography 01/2012; 113(1):98-105. · 0.57 Impact Factor
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    ABSTRACT: Our previous investigations of unirradiated ODS Eurofer by tomographic atom probe (TAP) revealed numerous nano-scaled features (nanoclusters) enriched in vanadium, yttrium and oxygen. In this work the effect of neutron irradiation on nanostructure behaviour of ODS Eurofer (9%-CrWVTa) was investigated. The irradiation was performed in the research reactor BOR-60 (Dimitrovgrad, Russia) where materials were irradiated at 330 degrees C to 32 dpa. TAP studies were performed on the needles prepared from parts of broken Charpy specimens. For all specimens except one, which was tested at 500 degrees C, the Charpy tests were performed at temperatures not exceeding the irradiation temperature. A high number density 2-4 x 10(24) m(-3) of ultra fine 1-3 nm diameter nanoclusters enriched in yttrium, oxygen, manganese and chromium was observed in the irradiated state. The composition of detected clusters differs from that for unirradiated ODS Eurofer. It was observed in this work that after neutron irradiation vanadium atoms had left the clusters, moving from the core into solid solution. The concentrations of yttrium and oxygen in the matrix, as it was detected, increase several times under irradiation. In the samples tested at 500 degrees C both the number density of clusters and the yttrium concentration in the matrix decrease by a factor of two. (C) 2010 Elsevier B.V. All rights reserved.
    Journal of Nuclear Materials 02/2011; 409(2):94-99. · 2.02 Impact Factor
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    ABSTRACT: Oxide dispersion strengthened steels possess better high-temperature creep and radiation resistance than conventionally produced ferritic/martensitic steels. This behaviour is mainly caused by the presence of highly dispersed and extremely stable oxide particles with diameters of a few nanometers. In this work the nanostructure of ODS Eurofer steel was investigated by means of tomographic atom probe and correlations with recent TEM and SANS studies were derived. The present investigation revealed nanoscaled clusters of typically 2 nm diameter containing not only yttrium and oxygen but also vanadium and nitrogen. Moreover, concentration of vanadium in particles was found to be higher than that of yttrium, which indicates the importance of these elements in cluster formation. The estimated average cluster number density is about 2 x 10(24) m(-3). These enriched zones might be evidently attributed to precursors of the larger precipitates observed by TEM. This conclusion is also supported by the similarities of the chemical composition inside enriched zones seen in both atomic probe and TEM data. (C) 2010 Elsevier B.V. All rights reserved.
    Journal of Nuclear Materials 01/2011; 409(2):65-71. · 2.02 Impact Factor
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    ABSTRACT: Since 2008 the ion beam irradiation modeling experiments for the testing of reactor materials radiation hardness are under development at the ITEP heavy ion RFQ injector with MEVVA ion source. Ion beam irradiation method has certain advantages for such tests. One of them is high speed of defect formation. Moreover, the irradiated samples can be investigated by traditional investigation methodic because they have not radioactivity induced. The special sample support with electrostatic deflector was constructed and installed at the injector output. The result of ion beam dynamics simulation throughout the deflector as well as the detailed description of the test facility is presented. The first experimental results are presented as well. They have been demonstrated promising results.
    The Review of scientific instruments 02/2010; 81(2):02B906. · 1.52 Impact Factor
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    ABSTRACT: The present work provides the analyses of embrittlement behavior and atom probe tomography study of nano-structure evolution of VVER-440 RPV materials under irradiation and re-irradiation. Specimens from VVER-440 weld with high level of cupper (0.16 wt.%) and phosphorus (0.027–0.038 wt.%) were irradiated in surveillance channels of Rovno Nuclear Power plant unit 1 (Ro-1). The embrittlement behavior has been assessed by transition temperature shift.
    ASME 2009 Pressure Vessels and Piping Conference; 01/2009
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    ABSTRACT: At present, the temperature-resistant steels with a rapid reduction of induced radioactivity appear to be a perspective structural material for new-generation nuclear and thermonuclear reactors. Special attention is paid to the nanostructural state of the elaborated materials. In this work, for the first time, there have been carried out tomographic atom-probe studies of the chromium ferritic-martensitic steel EK-181 (RUSFER EK-181) with 12% Cr. Spatial distributions of chemical elements in the investigated volumes of the material with an atomic resolution have been obtained. The dimensions of the investigated portions of the material are on the order of 10 × 10 × 30 nm3. There have been observed nanosized preprecipitates (nanoclusters), i.e., regions enriched in V, Cr, and N atoms, with characteristic sizes of about 3 nm.
    The Physics of Metals and Metallography 01/2009; 108(6):579-585. · 0.57 Impact Factor
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    ABSTRACT: Development of new materials for future energy facilities with higher operating efficiency is a challenging and crucial task. However, full-scale testing of radiation hardness of reactor materials is quite sophisticated and difficult as it requires long session of reactor irradiation; moreover, induced radioactivity considerably complicates further investigation. Ion beam irradiation does not have such a drawback, on the contrary, it has certain advantages. One of them is high speed of defect formation. Therefore, it provides a useful tool for modeling of different radiation damages. Improved understanding of material behavior under high dose irradiation will probably allow to simulate reactor irradiation close to real conditions and to make an adequate estimation of material radiation hardness. Since 2008 in ITEP the ion beam irradiation experiments are under development at the ITEP heavy ion RFQ HIP-1. The main objectives of this work are to study primary damage, cascade formation phenomena, phase stability and self-organization under irradiation. This research is carried out by means of tomographic atom probe and transmission electron microscopy. This linac provides accelerated beams of Cu2+, Fe2+, Cr2+ ions with current up to 10 mA and energy 101 keV/n. The first experiments with ion beam at the linac injector demonstrated promising results. The linac output beam line is now under upgrade. The results of beam extraction line adjustment for experiments with reactor materials are presented. The construction of controllable heated target is presented as well.
    01/2009;
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    ABSTRACT: Reduced activation ferritic/martensitic 12% Cr EK-181 steel (Fe-12Cr-2W-V-Ta-B-0.16C) was investigated using atom probe tomography after various regimes of heat treatment: annealing at 800–850°C, conventional normalizing-and-tempering (N&T), and combined heat treatment (quenching + thermal cycling + tempering). The data were obtained on the content and distribution of different chemical elements in the specimens after various heat treatments. It is shown that nanoclusters are formed in the matrix of EK-181 steel under conventional normalizing-and-tempering (N&T) heat treatment, enriched in V, Cr, and N. The average size of clusters is 2–4 nm and the number density is 3 × 1023 m−3.
    Inorganic Materials: Applied Research. 3(2).
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    ABSTRACT: Development of new materials for future energy facilities with higher operating efficiency is a challenging and crucial task. However, full-scale testing of radiation hardness of reactor materials is quite sophisticated and difficult as it requires long session of reactor irradiation; moreover, induced radioactivity considerably complicates further investigation. Ion beam irradiation does not have such a drawback, on the contrary, it has certain advantages. One of them is high speed of defect formation. Therefore, it provides a useful tool for modeling of different radiation damages. Improved understanding of material behaviour under high dose irradiation will probably allow to simulate reactor irradiation close to real conditions and to make an adequate estimation of material radiation hardness. ITEP heavy ion RFQ HIP-1 provides accelerated beams of Cu 2+ , Fe 2+ , Cr 2+ ions with current up to 4 mA and energy 101 keV/n. The results of beam extraction line adjustment for experiments with reactor materials are presented. The construction of controllable heated target is presented as well. The first experiments will be started at the beginning of 2009.Also, the low energy experiments are carried on at the HIP-1 injector. The construction of target for low energy experiments is presented as well. The main objectives of this work are to study primary damage, cascade formation phenomena, phase stability and self-organization under irradiation. This research is carried out by means of tomographic atom probe and transmission electron microscopy.
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    ABSTRACT: The nanostructure of Eurofer97 reduced activation 9% chromium ferritic-martensitic steel (9Cr1W0.2VTa0.1C) irradiated by neutrons in BOR-60 reactor at a temperature of 332°C up to 32 dpa is studied by atom probe tomography. A high number density (1024 m−3) of ∼3–5 nm clusters enriched in chromium, manganese, and silicon atoms is found in the material. An analysis of the redistribution of chemical elements in the material shows that the steel matrix becomes substantially depleted of chromium.
    Inorganic Materials: Applied Research. 4(2).