Персона: Савельев, Максим Дмитриевич
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Development of the technology of obtaining the composite based on the "magnesium-bone substance" for biodegradable implants by the method of powder metallurgy
© Published under licence by IOP Publishing Ltd.This work reports on the development of a composite "magnesium (Mg)-bone substance (HA)" for a biodegradable implant using powder metallurgy methods. In the course of the work, experiments were performed in two different types of a powder compaction: sintering this composite by standard compaction method and the spark-plasma sintering method (SPS). The optimum parameters for compacting the powder mixture were selected, the initial percentage of open porosity after sintering samples was calculated, X-ray microanalysis was performed, and the microstructures of the samples, which had been obtained by using various powder metallurgy methods, were compared.
МОДИФИКАЦИЯ ПОВЕРХНОСТИ ВОЛЬФРАМА ПОД ВОЗДЕЙСТВИЕМ ГЕЛИЕВОЙ ПЛАЗМЫ С ПРИМЕСЬЮ ИНЕРТНЫХ ГАЗОВ
Одним из приоритетных направлений в области термоядерных исследований является контроль уровня плазменно-тепловой нагрузки на внутрикамерные элементы установок магнитного удержания горячей плазмы. Постепенное развитие технологии напуска примеси инертного газа (He, Ne, Ar) в процессе плазменного разряда в установках типа токамак и стелларатор [1, 2] как средства радиационного охлаждения периферии плазмы, предъявляют новые требования по контролю состояния поверхности обращённых к плазме элементов.
Joining tungsten with steel for DEMO: Simultaneous brazing by Cu-Ti amorphous foils and heat treatment
© 2020Development of a reliable technology to join tungsten with steel is essential for DEMO application; however, it is difficult due to large differences in their physical properties. To solve this problem, high-temperature brazing was carried out. Cu-Ti brazing alloys, which were rapidly solidified into foil, were used together with a compensating vanadium interlayer, so the EK-181 steel/Cu-28Ti/V/Cu-50Ti/W and EK-181/Cu-50Ti/V/Cu-50Ti/W brazed joints were obtained. The microstructures of the seams were investigated by optical microscopy, SEM (EDX, EBSD) and synchrotron XRD. Thermocycling and shear strength tests showed that Cu-28Ti wt. % brazing alloy ensures a firmer joint compared to Cu-50Ti wt. %. The Cu-28Ti wt. % brazing alloy was used to perform high-temperature brazing in the brazing mode equivalent to traditional EK-181 steel heat treatment. It showed that every step of the heat treatment affected the microstructures and the shear strength.
High-temperature brazing of tungsten with steel by Cu-based ribbon brazing alloys for DEMO
© 2019 Elsevier B.V. The designs of DEMO components require the joining of low-activation steel (for example RUSFER EK-181, EUROFER, etc.) with tungsten. One of the most critical parameters is the thermal expansion mismatch between tungsten and steel, which can lead to the failure of components during use or even after manufacturing.In this paper, high-temperature brazing of EK-181 steel with tungsten was carried out. Pure copper was used for the direct joining of steel with tungsten. Brazing alloys based on copper (Cu–Ge and Cu–Ti) rapidly quenched into ribbon were used with a vanadium interlayer. Brazing was carried out in vacuum furnaces at 1100 °C for 20 min. The structural-phase states of the joints obtained were studied, the microhardness measured, shear strength tests carried out and thermocycling tests performed in the range 700–25 °C.
Dependence of the thermophysical properties of alloys of the Fe-Cr-Al-Si system on the composition and temperature
Brazing tungsten/tantalum/RAFM steel joint for DEMO by fully reduced activation brazing alloy 48Ti-48Zr-4Be
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.To create a DEMO reactor, it is necessary to develop high-quality technology to join tungsten with reduced-activation ferritic-martensitic (RAFM) steel (Rusfer, Eurofer, CLF-1, etc.). Diffi-culties arise in their direct connection due to the large difference in the coefficient of thermal expan-sion (CTE). To suppress the difference of CTE, intermediate interlayers are usually used, such as vanadium or tantalum, and brazing is a prospective technology to conduct the joining. The vast majority of works represent copper-or nickel-based brazing alloys, but their applicability is under significant discussion due to their activation properties. That is why, in this work, fully reduced activation 48Ti-48Zr-4Be wt.% brazing alloy was used. The following joint was made: Rusfer steel/48Ti-48Zr-4Be/Ta/48Ti-48Zr-4Be/W. The brazing was successfully carried out under a mode providing thermal heat treatment of Rusfer. Through EDS and EBSD analysis, the microstructure of the joint was determined. Shear strength of the as-joined composition was measured as 127 ± 20 MPa. The joint endured 200 thermocycles in the temperature range between 300-600 °C, but the fillet regions degraded.
Regularities of Formation of Lattice Structures Fabricated by Selective Laser Melting of Powdered 03Kh16N15M3 Steel
© 2020, Pleiades Publishing, Ltd.Abstract: This article discusses adjustment of processing modes of selective laser melting of powdered 03Kh16N15M3 steel allowing fabrication of lattice structures with steady parameters. On the basis of statistical analysis of sizes of cells, ribs, and nodes in cross section parallel to the growth direction of lattice structures of two sizes of ribs and voids (400 × 1000 and 300 × 600 μm), the process variables providing fabrication of items with the most stable sizes along the height of the structure have been determined. The sizes of the main elements of the lattice structure have been determined using a scanning electron microscope; the crystallographic texture and material structure have been determined using X-ray structural analysis. It has been determined that increase in laser power leads to increase in distortions in crystalline structure and decrease in the lattice constant of the material of lattice structures. The highest distortions of the structure have been detected in ribs of lattice structures as well as in items with smaller sizes of ribs and voids. The material of the considered lattice structures is characterized by axial texture, for which crystallographic axes <100> are oriented parallel to the growth direction. The degree of manifestation of the axial texture component depends on the laser power used for growing of lattice structures. The samples obtained by minimum radiation power are characterized by a scattered axial texture, which is dictated by an increase in the number of chaotically oriented grains with a simultaneous decrease in the bulk of strictly oriented columnar crystals, located mainly in the vicinity of the axis of the ribs of the lattice structure. The texture sharpness in lattice samples with voids of small size is higher than that in samples with voids of large size.