Structural-phase State Research Articles

Плёнки FeZrN: статические и СВЧ магнитные свойства

The phase-structural state, magnetic structure parameters, static and microwave magnetic properties of Fe81 – 74Zr2 – 5N17 – 21 films prepared by reactive magnetron deposition were studied. As the Zr and N contents increase, the film structure changes from, so-called, mixed structure (grain size 3 – 6 nm of nanocrystalline α-Fe(Zr,N) + fcc nitride) to amorphous one. The film magnetic structure parameters (effective anisotropy field of stochastic domains D1/2〈Ha〉 = 11.8 ± 8 Oe and effective local anisotropy field D1/2Ha = 880 ± 700 Oe), saturation magnetization Ms (1.8 ± 0.3 T), coercive field Hc (11 ± 2 Oe), and the real permeability µ′ (80 ± 30), retaining its value at frequencies up to 3 GHz, were determined. The values of the initial permeability µ0 (70 ± 21) obtained from the hysteresis and the real permeability µ′ (80 ± 30) obtained from microwave measurements are in good agreement. The correlation between the static magnetic properties, the stochastic magnetic structure parameters and the real permeability µ′ was considered. There is no any sign on ferromagnetic resonance in the studied frequency range. However the Acher’s coefficient value (less than 0.38) for this frequency range indicates the possibility of ferromagnetic resonance at higher frequencies.

Electrocatalytic activity and surface oxide reconstruction of bimetallic iron-cobalt nanocarbide electrocatalysts for the oxygen evolution reaction.

For renewable energy technology to become ubiquitous, it is imperative to develop efficient oxygen evolution reaction (OER) electrocatalysts, which is challenging due to the kinetically and thermodynamically unfavorable OER mechanism. Transition metal carbides (TMCs) have recently been investigated as desirable OER pre-catalysts, but the ability to tune electrocatalytic performance of bimetallic catalysts and understand their transformation under electrochemical oxidation requires further study. In an effort to understand the tunable TMC material properties for enhancing electrocatalytic activity, we synthesized bimetallic FeCo nanocarbides with a complex mixture of FeCo carbide crystal phases. The synthesized FeCo nanocarbides were tuned by percent proportion Fe (i.e. % Fe), and analysis revealed a non-linear dependence of OER electrocatalytic activity on % Fe, with a minimum overpotential of 0.42 V (15-20% Fe) in alkaline conditions. In an effort to understand the effects of Fe composition on electrocatalytic performance of FeCo nanocarbides, we assessed the structural phase and electronic state of the carbides. Although we did not identify a single activity descriptor for tuning activity for FeCo nanocarbides, we found that surface reconstruction of the carbide surface to oxide during water oxidation plays a pivotal role in defining electrocatalytic activity over time. We observed that a rapid increase of the (FexCo1-x)2O4 phase on the carbide surface correlated with lower electrocatalytic activity (i.e. higher overpotential). We have demonstrated that the electrochemical performance of carbides under harsh alkaline conditions has the potential to be fine-tuned via Fe incorporation and with control, or suppression, of the growth of the oxide phase.

Structural–Phase State of a Surface of Electron-Beam Treatment of a Steel Subjected to Electroexplosive Aluminizing

Structural–Phase State of a Surface of Electron-Beam Treatment of a Steel Subjected to Electroexplosive Aluminizing

Structural–Phase States of an Al–Fe–Co–Cr–Ni HEA Coating Formed on 5083 Alloy

Structural–Phase States of an Al–Fe–Co–Cr–Ni HEA Coating Formed on 5083 Alloy

Nanostructured TiAlCuN and TiAlCuCN coatings for spacecraft: effects of reactive magnetron deposition regimes and compositions.

Spacecraft are exposed to a number of factors in the outer space: irradiation by electron flows, high-energy ions, solar electromagnetic radiation, plasma irradiation, and a stream of meteorite particles. All these factors initiate various physical and chemical processes in spacecraft materials, which can eventually lead to failure. To ensure reliable operation of spacecraft, it is necessary to use protective coatings and special radiation-resistant materials. TiAlCuN and TiAlCuCN coatings were formed by reactive magnetron sputtering on different substrates: single-crystal silicon and Titanium Grade 2 wafers. Nitrogen was used as a reactive gas to form nitride coatings and acetylene was used to form carbonitride coatings. The elemental composition was studied by energy-dispersive X-ray (EDX) spectroscopy. The structural-phase state of the coatings was examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Mechanical properties, such as hardness and Young modulus, were investigated by nanoindentation using a CSM Instruments Nanohardness Tester NHT2. The influence of deposition parameters, such as Ti and Al contents, the degree of reactivity α, and carbonitride formation on the structure and their mechanical properties were considered. It was detected that Cu addition to the coatings has effects on crystallite and growth column size refinement in comparison with the TiAlN and TiAlCN analogues due to its segregation along crystalline boundaries, and thus, imparts better mechanical characteristics. The hardness of TiAlCuN and TiAlCuCN coatings varies in the range of H = 25-36 GPa and Young modulus - E = 176-268 GPa. The impact strength index and the H/E* ratio, as well as the plastic deformation resistance index H3/E*2, were calculated. Due to their high mechanical properties, the formed nitride and carbonitride coatings are promising for use in space technologies.

Термическая стабильность структурно-фазового состояния алюминия и сплавов системы Al – Si, легированных атомами циркония при воздействии компрессионных плазменных потоков

The results of structural-phase state investigations of Аl, Al – 12,6 wt. % Si – 0,1 wt. % Fe and Al – 12,6 wt. % Si – 0,5 wt. % Cu – 2,7 wt. % Mg – 0,3 wt. % Ni – 0,3 wt. % Fe – 0,2 wt. % Mn alloys surface layers alloyed by zirconium atoms under action of compression plasma flows are presented. The formation of metastable compounds Al3Zr with L12 structure and (Al,Si)3Zr with D022 structure in the alloyed layers of aluminum and silumin samples, respectively, was found. Alloying with zirconium atoms makes it possible to increase the microhardness of surface layer in 1.4 – 3 times. Thermal stability of the structure and phase composition of alloyed layers at 550 °C was investigated. The transformation of Al3Zr – L12 into Al3Zr – D023 phase in aluminium and (Al,Si)3Zr disintegration with ZrSi2 in Al – Si alloys was observed during annealing. The formed surface layers had elevated temperature strength.

The Structure and Properties of Wrought Al–Mg–Sc Aluminum Alloys with Different Scandium Content

Round ingots 110 mm in diameter and cold-rolled sheets 2 mm in thickness, which were made of experimental Al–Mg–Sc alloys containing different scandium content (0.07, 0.20 wt %), have been studied. Transmission electron microscopy and thermodynamic simulation have been used to investigate the peculiar-ities of the structural-phase state of the material. A reduction in scandium content from 0.20 to 0.07% has been found to result in a twofold increase in the grain size in ingots, a 46% drop in hardening of ingots after homogenization, and a 10–20% decrease in the strength of annealed sheets, which has been caused by a smaller amount of the key phase, Al3(Sc, Zr). A good level of strength characteristics of experimental annealed sheets made of alloy with low scandium content 0.07 wt % (σu 400 MPa, σ0.2 300 MPa) has been achieved and it is higher than that of the traditional AMg6 alloy (σu 350 MPa, σ0.2 150 MPa).

Влияние длительной эксплуатации на структурно-фазовое состояние заэвтектоидной рельсовой стали

Влияние длительной эксплуатации на структурно-фазовое состояние заэвтектоидной рельсовой стали

Dynamics of moisture content and sowing qualities of seeds in rice varieties during post-harvest ripening and storage

Rice seeds at each stage of ripening are characterized by a certain state, structure and moisture. Such properties of rice as germination, nature, quality and duration of storage depend on moisture content. Biochemical processes in the grain do not end at the filling stage, but continue for some post-harvest period. To safely preserve the rice gene pool, it is necessary to clarify the effect of seed maturity and storage time on seed quality. The varietal characteristics of rice seeds were studied using 8 Kuban varieties harvested on days 35 and 45 after flowering. The structural-phase state of freshly harvested grain and after 5, 10 days of ripening in natural conditions at room temperatures, and then the dynamics of sowing qualities after 1, 6 and 10 months of storage are discussed. The following parameters were studied: moisture, germination, length of the seedling and seed root, mass of 1000 grains. Differences in the moisture yield of grain of different degrees of maturity, varieties with different types of grain are shown. The results of the evaluation of rice physico-chemical indicators at the end of post-harvest ripening are presented. Varieties with slow moisture yield during ripening were distinguished by increased grain size: Yakhont, Rubin, Thaibonne and Zlata. The germination of seeds increased as they ripened, compared with freshly harvested ones, after a month it increased by almost 50%, and reached its maximum value by 6 months of storage, after 10 months, on average, germination for the group of varieties has already decreased by 6%. The stage of seed harvesting significantly influenced the germination rates.

Structural-phase transformations during nitro oxidation of steels and surface properties

Structural and phase changes in the surface diffusion layer during gas nitriding of steel were studied, with the formation of a crystallographic structure of the nitride layer for subsequent oxidation in water vapor. The conditions for forming carbides and nitrocarbides with simultaneous diffusion of nitrogen and decarburization of the steel matrix are determined depending on the nitrogen potential of the saturating medium. The structural-phase states of the surface diffusion layer with a stepwise change in the nitrogen potential during nitriding at the first stage and followed by oxidation at the second stage, the formation of a surface oxide layer, as well as the conditions for participation in mutual diffusion processes of carbon in the nitride layer, decarburized from the steel matrix with the formation compositions of modified nitride phases. The nitride-oxide layer’s corrosion properties and gradient properties in various structural-phase states of nitride phase compositions have been studied.

Особенности микроструктуры и микротекстуры среднеуглеродистой стали, подвергнутой сероводородному растрескиванию под напряжением

Increasing the resistance of steel products to sulfide stress cracking (SSC) is one of the topical issues of the oil and gas industry. Among various factors determining the SSC resistance of a material is the structure-phase state of the material itself and the crystallographic texture associated with it. This paper analyzes these features using the scanning electron microscopy (SEM), transmission electron microscopy (TEM), and microroentgen electron backscattered diffraction (EBSD) techniques. As the research material, a production string (PS) coupling made of medium-carbon steel was selected, which collapsed by the mechanism of hydrogen embrittlement and subsequent SSC. For the first time, by the SEM method, using the location and mutual orientation of cementite (Fe3C) particles, at high magnifications, the authors demonstrated the possibilities of identifying the components of upper bainite, lower bainite, and tempered martensite in steels. The presence of the detected structural components of steel was confirmed by transmission electron microscopy (TEM). Using the EBSD method, the detailed studies of microtexture were conducted to identify the type and nature of the microcrack propagation. It is established that the processes of hydrogen embrittlement and subsequent SSC lead to the formation of {101} <0¯10>, {100} <001>, {122} <2¯10>, {013} <211>, {111} <¯100>, {133} <1 ̅2 ̅1>, {32 ̅6 ̅} <201> grain orientations. It is shown that the strengthening of orientations of {001} <110>, {100} <001>, {112} <111>, and {133} <1 ̅2 ̅1> types worsens the SSC resistance of the material. Using the EBSD analysis method, the influence of coincident site lattice (CSL) grain boundaries on the nature of microcrack propagation is estimated. It is found that the Σ 3 CSL grain boundaries between the {122} <2¯10> and {111} <¯100>, {012} <1 ̅1 ̅0>, {100} <001> plates of the upper bainite inhibit the microcrack development, and the Σ 13b, Σ 29a, and Σ 39a CSL grain boundaries, contribute to the accelerated propagation of microcracks. For comparative analysis, similar studies were carried out in an unbroken (original) coupling before operation.

Magnetic anisotropy of Nanostructured Fe-Ni-C Coating Produced by Electroless Deposition

The structural and magnetic properties of nanostructured Fe100-xNix-C (0<x<100) coatings produced by electroless plating with different carbohydrates as reducing agents have been investigated. The phase-structural state of the films was studied by diffraction and electron microscopy. The Ni concentration ranges of FCC and BCC phases existence in electroless deposited films were determined. The surface morphology, saturation magnetization, local magnetic anisotropy field and coercivities of films are dependent on the iron content and type of reducing agent. The correlation between coercivity Hc and the anisotropy field of the magnetic stochastic domain which were established by correlation magnetometry suggests that the magnitude of Hc is mainly determined by this anisotropy. Keywords: 3d-metal alloys, the approach to saturation magnetization law, coercivity.

Магнитная анизотропия наноструктурированных покрытий Fe-Ni-C, полученных методом химического осаждения

The structural and magnetic properties of nanostructured Fe-Ni‒C coatings produced by electroless plating with different carbohydrates as reducing agents have been investigated. The phase-structural state of the films was studied by X-ray diffraction and electron microscopy. The Ni concentration ranges of FCC and BCC phases existence in electroless deposited Fe-Ni‒C films were determined. The surface morphology, saturation magnetization, local magnetic anisotropy field and coercivities of FeNi-C films are dependent on the iron content and type of reducing agent. The correlation between coercivity and the anisotropy field of the magnetic stochastic domain which were established by correlation magnetometry suggests that the magnitude of Hc is mainly determined by this anisotropy

Mechanisms of hardening of 12 % chromium ferritic-martensitic steel EP-823

Based on experimental data on microstructure parameters of the reactor high-strength high-chromium (12 % Cr) ferritic-martensitic steel EP-823, the authors identified the main factors responsible for its strength properties. The hardening mechanisms of this steel were analyzed after processing according to the modes that provide different level of steel strength properties. Traditional heat treatment (THT) and promising modifying high-temperature thermomechanical treatment (HTMT) are considered. The main mechanisms of steel hardening, regardless of the processing mode, are: dispersed hardening by nanoscale particles of the MeX type (Me = V, Nb, Mo; X = C, N) by the Orovana mechanism; grain-boundary hardening by high-angle boundaries of martensitic blocks and ferrite grains; substructural hardening by small-angle boundaries of martensitic lamellae; dislocation hardening by increased dislocation density. HTMT mode, which includes hot deformation in the austenitic area, leads to a significant modification of the structural-phase state of steel relative to THT: a decrease in the average size of blocks and lamellae of martensite, as well as ferrite grains, an increase in the density of dislocations and the volume fraction of nanoscale particles of the MeX type. At the same time, the corresponding contributions to value of the steel yield strength from grain boundary, substructural and dispersed hardening increase by 1.2, 1.3 and 1.8 times in comparison with THT. The relative contributions of the considered hardening mechanisms to the yield strength of ferritic-martensitic steel EP-823 were discussed. The values closest to the experimental yield strength after two treatment modes studied are obtained when the Langford-Cohen model is used to estimate the magnitude of substructural hardening.

STRUCTURAL-PHASE STATE AND METAL FRACTURE SURFACE OF WELDS MADE WITH THE USE OF NEW MATERIALS BASED ON TECHNOGENIC RAW MATERIALS

The structural-phase state and the metal fracture surface of 09G2S steel welds made using new welding materials based on technogenic raw materials of metallurgical production (silica manganese slag and aluminum electrofilter dust) were studied by scanning and transmission electron microscopy methods. The production of welded joints was carried out in laboratory conditions using welding wire of the Sv-08GA brand on the equipment of the scientific and production center "Welding Processes and Technologies" of SibSIU. Quantitative analysis of the parameters of the structure and dislocation substructure of the weld metal was performed, using the equipment of the Institute of High-current Electronics SB RAS (Tomsk). The contributions of scalar and excessive dislocation density to the strength of the weld metal are estimated. It is established that the main metal phase of the studied welds (regardless of the introduction of the additive) is a solid solution based on α-iron (ferrite, BCC crystal lattice, α-phase). In addition to α-iron, particles of iron carbide (cementite) and (mainly in the sample without additives) iron silicide of the composition Fe3S are present in the weld metal. Analyzing electron microscopic images of the structure of the weld metal, it was noticed that the narrowest contours are formed at the interfacial boundaries of the inclusion – matrix. Such inclusions detected by transmission electron microscopy methods may be cementite particles located in the volume and at the boundaries of ferrite grains, and iron silicide particles of rounded (spherical) shape located in the volume of ferrite grains. It is revealed that the inclusions of the second phase present in the weld metal are stress concentrators and can be centers of microcrack nucleation under mechanical action on the material.

INFLUENCE OF THE GRADIENT ZONE EXTENT OF THE FUNCTIONAL GRADIENT PRODUCT OF THE CU/AL SYSTEM ON THE STRUCTURAL-PHASE STATE AND MECHANICAL PROPERTIES

The formation of functional gradient Cu/Al materials with a continuous intermetallic surface layer by electron beam additive manufacturing is associated with the formation of a number of inhomogeneities and defects in the structure. The main obstacles to obtaining stable and defect-free FGM structures on the surface of the copper base are the difference in the coefficients of thermal expansion of copper and aluminum at the boundary with the formation of intermediates, cracks and delaminations. The formation of a smooth gradient from copper to intermetallic Cu/Al layers allows to avoid the formation of cracks and delaminations. In the work, defect-free functional gradient Cu/Al materials with different gradient zone widths were obtained using electron beam additive technology. The structural-phase state and mechanical properties of FGM Cu/Al over the entire height of the printed material are investigated. It is established that the Cu/Al gradient zone of FGM consists of the phases α-Cu, Cu4Al, Cu3Al and Cu9Al4. It is established that the width of the gradient zone affects the volume fraction of CuxAly intermetallic phases, which, in turn, determine the magnitude of the elongation at a constant value of the tensile strength (305 ± 10 MPa). The microhardness values increase sharply in the gradient zone and have an uneven distribution due to the formation of Cu4Al, Cu3Al and Cu9Al4 intermetallides. It is shown that the upper part of the Cu/Al FGM, consisting of 67 % Cu and 33 % Al (vol.), demonstrates a sharp drop in mechanical properties, which is probably due to the formation of the Cu9Al4 phase, the volume fraction of which prevails compared to other intermetallic phases of the CuxAly system.

Formation of TiN coatings by air plasma spraying

Titanium nitride (TiN) coatings were obtained on the surface of 12Kh18N10T steel by air plasma spraying (APS) of TiN powders using an arc plasmatron made by the authors. The plasmatron has a node of circular input and gas-dynamic focusing of the powder and the output apertures of the nozzle-anode are made in the form of rectangular narrowing-expanding channels (No.34334 RK: IPC H05H 1/42). A study of operation modes of a plasmatron for spraying of powder coatings was carried out. The structural-phase state, microhardness and wear resistance of TiN coatings were systematically investigated. The optimum APS operating mode for deposition of TiN powder was determined: current 250 A, voltage 68 V, argon gas flow 34 L/min, spraying distance 150 mm. To reduce the oxidation of TiN powder in the APS process, a method of creating a nitrogen environment at the outlet of the anode nozzle, nitrogen flow rate 2.3 bar was used. The results of structural analysis showed that TiN is the main phase of the coating. The mechanism of formation of TiN structures was characterized by analyzing SEM results of TiN coating surface morphology and TiN droplets sprayed on the surface of the sample. The results showed that the TiN(1) coating has better wear resistance than the TiN(2) and TiN(3) coatings. The cross-sectional and longitudinal microhardness of the TiN coating was investigated. The highest cross-sectional hardness of TiN coating is 1250 HV0.1, which is in accordance with mode 1.

Технологічні рішення щодо одержання якісних виливків з високохромистих чавунів

The article presents the results of research conducted to check the effect of alloying with manganese and molybdenum and modification of high-chromium cast iron with niobium on the formation of its structure during heat treatment. The effect of heat treatment in the temperature range of 450...900°C and normalization at a temperature of 1000...1200°C on structural transformations, hardness and wear resistance of complex alloyed high chromium cast irons was studied. The research material was samples of cast iron (1.8...2.3% C and 12...20% Cr), doped with manganese, molybdenum (2...4% Mn, 0.6...1.2% Mo) and modified with niobium, it was checked microstructures of samples in the cast state and when heated to temperatures of 650 °C and 780 °C with the following content of elements: С – 2.07 %, Cr – 19.7 %, Mn – 3.55 %, Mo – 1.02 %, Nb – 0.3%, Si – 0.6%. Experiments were carried out in the temperature ranges: 450...500 °C; 500...550 °C; 600...650 °C; 700...900°C; 1000...1200 °C with varying holding time from four to twenty hours. The hardness of cast iron is 40-42 HRC. The microhardness of austenite is 340-420 Nμ. The influence of the degree of alloying and the number of individual alloying elements in the alloy on the beginning of the austenite transformation was established. When heated to 500...550 °C with an increase in the chromium content in the alloys, the time to the beginning of the transformation increases. In alloys with a chromium content of 17.7%, the beginning of transformation was observed after 4 hours, while in alloys with a chromium content of about 22%, the beginning of transformation was detected after 9...10 hours of exposure. During normalization (1050...1100°C), the Me7C3 → Me23C6 transition process occurs faster in chromium cast irons with molybdenum than in alloys with tungsten. With a molybdenum content of more than 0.6%, Me7C3 carbide is completely transformed into Me23C6, which in the range of 0.6...1.2% is the only carbide phase. It was found that the amount of martensite depends on both the heating temperature and the cooling rate. When cooling at a rate of 30 °C/h, less martensite is formed in the cast iron structure than when cooling at a faster rate of 70 °C/h. It was found that in the cast state, the structure of high-chromium cast irons consists of austenite and austenite-chromium carbide eutectic, which contains trigonal carbide (Cr,Fe)7С3. As a result of heating cast iron in the temperature range of 450...900°C and normalization at a temperature of 1000...1200°C, austenite has a different ability to disintegrate, and this affects the phase composition of cast irons, their structure and properties. The transformation into austenite begins with the release of a dispersed carbide phase (Cr,Fe)23С6 at a temperature of 650°C. It was determined that the experimental complex-alloyed high-chromium cast irons in the cast state had a hardness of 40...47 HRC, and after normalization at a temperature of 1050...1100°C with a holding time of 1 h - 55...62 HRC. At the same time, about 30% of austenite, martensite and carbide phase remain in cast iron. It was determined that normalization at a temperature of 1050...1100°C with a holding time of 1 hour contributes to the formation of a metastable structure with high resistance to destruction with the content of excess austenite, martensite and the carbide phase (Cr,Fe)23С6. Keywords: alloying elements, cast state, high-chromium cast iron, heat treatment, phase-structural state.

Structure–Phase State and Properties of HVAF Quasi-Crystalline Al–Cu–Fe Coating Produced from Water-Atomized Powder

Structure–Phase State and Properties of HVAF Quasi-Crystalline Al–Cu–Fe Coating Produced from Water-Atomized Powder

Synthesis of Ti21.5V40Cr38.5 alloy by abnormal glow discharge plasma

The paper describes the structural-phase state and sorption characteristics of the Ti21.5V40Cr38.5 alloy synthesized by melting in abnormal glow discharge plasma and arc melting. X-ray diffraction patterns showed the presence of the main TiVCr phase with a body-centered cubic (bcc) lattice and Ti2O phase with a hexagonal close packed (hcp) lattice. The maximum hydrogen capacity of the samples obtained by melting in abnormal glow discharge plasma after 3 cycles was 3 wt%.