S. V. Rogozhkin

ITEP MEVVA ion beam for reactor material investigation.

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.

Atom probe study of radiation induced precipitates in Eurofer97 Ferritic-Martensitic steel irradiated in BOR-60 reactor

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.

Surface modification of ferritic steels using MEVVA and duoplasmatron ion sources

Metal Vapor Vacuum Arc (MEVVA) ion source (IS) is a unique tool for production of high intensity metal ion beam that can be used for material surface modification. From the other hand, the duoplasmatron ion source provides the high intensity gas ion beams. The MEVVA and duoplasmatron IS developed in Institute for Theoretical and Experimental Physics were used for the reactor steel surface modification experiments. Response of ferritic-martensitic steel specimens on titanium and nitrogen ions implantation and consequent vacuum annealing was investigated. Increase in microhardness of near surface region of irradiated specimens was observed. Local chemical analysis shows atom mixing and redistribution in the implanted layer followed with formation of ultrafine precipitates after annealing.

Kinetics of α’-phase growth and coagulation under thermal aging of Fe–22% Cr alloy

Considered in the article, α’-phase growth and coagulation stages under 500°С thermal aging of Fe–22% Cr binary alloy have been investigated on the atomic scale level, with atom probe tomography being applied. α’-phase appearing precipitates are shown to be separated in space. In addition, after 100-hour thermal aging the nucleation stage evolves into the growth and coagulation stage of α’-phase precipitates, with their number density being decreased simultaneously. Deviation of time dependences from Lifshitz-Slezov theory is revealed in Fe–22% Cr supersaturated solid solution alloy.

Microstructure of Ti–5Al–4V–2Zr alloy in the initial condition and after irradiation with titanium ions

Chemical analysis of phases and inclusions in a specimen of Ti–5Al–4V–2Zr titanium alloy in the initial state and after irradiation with titanium ions up to the radiation damage dose of ~1 dpa at 260°C was carried out and the microstructure was studied. Microstructural analysis was performed by the methods of transmission electron microscopy, energy dispersion X-ray spectroscopy, and atom probe tomography. Results of the chemical analysis of the matrix α phase and inclusions of β phase grains are given. It is shown that the α phase is enriched in aluminum up to 10 at % and the β phase is enriched in vanadium up to 20 at % in the initial state in the Ti–5Al–4V–2Zr alloy. Heavy ion irradiation induces the formation of dislocation loops of 3 to 12 nm with the number density of ~1022 m–3. A high number density (up to ~1024 m–3) of nanoscale precipitations with the average size of ~2 nm is formed during alloy irradiation in the α phase.

Atom Probe Tomography Analysis of Materials using Femtosecond-Laser Assisted Evaporation

We study the possibilities of the chemical analysis of materials with determination of the positions of individual atoms of various chemical elements in a sample using an APPLE-3D atom probe tomograph with femtosecond-laser assisted evaporation, developed at the Institute of Theoretical and Experimental Physics of the National Research Center “Kurchatov Institute.” The results of investigations of ferritic-martensitic steels and an aluminum alloy are presented; the characterization and visualization of features with a size on the order of 10 nm are demonstrated.

Study of Nanostructure of Ferritic-Martensitic Steel ChS-139 in Initial State and after Fe Ion Irradiation

The chemical element distributions and the fine structure were studied using atom probe tomography in ChS-139 steel (Fe–12Cr–Nb–Mo–W–V–N–B) after conventional heat treatment (normalizing at 1190°C for 25 s and subsequent tempering at 720°C for 2 h) and after subsequent Fe ion irradiation at room temperature up to the damage doses of 8 and 16 displacements per atom (dpa). A large number of nanosized clusters (~1023 m−3) enriched in chromium, vanadium, nitrogen, and niobium were found throughout the Ch-139 steel after conventional heat treatment. The chemical element distribution in the M23C6 carbide, Nb2(C, N) and M6(C, N) carbonitride phases, pre-precipitates of M6X carbide phases, and the Cottrell atmosphere were studied. The changes in the cluster composition and sizes resulting from irradiation at room temperature were found. An increase in the cluster sizes upon irradiation was accompanied by a reduction in the concentrations of chromium, vanadium, nitrogen, and niobium.

Study of nanostructure of experimental Ti–5Al–4V–2Zr alloy

The microstructure and chemical composition of phases and inclusions in Ti–5Al–4V–2Zr alloys are studied in the initial state, after irradiation by titanium ions to radiation damage dose of ~1 dpa at 260°C, and after thermal aging at 450°C for 1000 h. Microstructural studies are carried out using scanning electron microscopy and atom probe tomography. Phase analysis is performed using energy dispersive X-ray spectroscopy. Chemical analysis of grains of the matrix phase and β-phase is presented. Spatial distribution of chemical elements in α- and β-phase lamellae is analyzed by atom probe tomography. Formation of nanosized vanadium pre-precipitates in the α-phase is observed in irradiated material.