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The features of phase formation during the joint aluminothermic reduction of titanium, niobium, tantalum, and vanadium from their oxides are studied using thermodynamic modeling and differential thermal (DTA) and X-ray diffraction phase analysis. Using computer thermodynamic modeling made it possible to predict the optimal temperature conditions in the metallothermic process, the composition and ratio of the reagents in the charge, the behavior of the elements, and the sequence of the phase formation. To identify the kinetic and thermochemical components of the process, thermodynamic calculations are supplemented by differential thermal studies using combined scanning calorimetry. An analysis of the theoretical and experimental data shows that the interaction of aluminum with titanium dioxide proceeds through the stage of formation of titanium monoxide and results in the formation of TixAly intermetallic compounds of various compositions (TiAl3, TiAl, and Ti2Al) depending on the Al to TiO2 ratio in the batch. When titanium dioxide is partially replaced by niobium, tantalum, and vanadium oxides, the metallothermic process under interactions in the Al–TiO2–Nb2O5, Al–TiO2–Ta2O5, and Al–TiO2–V2O5 systems is of the similar character; enters the active phase after the formation of liquid aluminum; is accompanied by exothermic effects; and is characterized by the priority formation of titanium aluminides and binary and ternary intermetallic aluminum compounds with rare refractory metals of group V such as AlNb3, Al3Nb, Al3Ta, Al3(Ti1 – х,Taх), Al3(Ti,Ta), and Al3(Ti0.8V0.2). The joint conversion of titanium dioxide and rare refractory metal pentoxides during the reduction process is affected through sequential and parallel stages of the formation of simple and complex element oxides with low oxidation states.

Tantalum and palladium were added to Inconel 718 at the expense of Nb content to study resultant microstructure and mechanical properties in hot-worked and annealed condition. An increase in {100} peak intensity along with a concomitant decrease in {111} peak intensity was observed with decreasing Nb content. Ta-containing alloys exhibited annealing twins and annealing twin density showed a direct relationship with Ta content. Overall, alloying additions improved strength as well as ductility except the alloy containing only Ta which was less strong than Inconel 718. The alloy containing Ta as well as Pd exhibited highest toughness and lowest Rockwell hardness value.

A novel 3d transition metal high entropy alloy (3d TM HEA), CoCrCuNiTi, was exploited by Ti addition into a common 4-elemental group of CoCrCuNi. Its phase constitution, microstructure, and compressive properties in as-cast and annealed conditions were investigated. The studied alloys in both states were composed of a complex multiphase structure, including two BCC phases, one FCC phase, one cubic laves phase, and one HCP Ni3Ti phase. The two BCC phases took up around 50 vol % in total, and the other three phases occurred within the remaining regions. The majority of the BCC phases were attributed to the promising ultimate compressive strength of the studied alloys in both conditions (as-cast: 2.53 GPa, annealed: 2.22 GPa). Furthermore, an outstanding hardness of 694 HV was obtained in the as-cast alloy, implying that no strong relationship was exhibited among the hardness, phase constituent, or valence electron concentration (VEC) in the CoCrCuNi-base HEAs system.

A comprehensive study of the features of physical and mechanical processes occurring in the deformation zone of metal during continuous extrusion is carried out with rectangular Cu-ETP buses 10 × 60 mm in size. With the use of finite element computer simulation, values of the power parameters of the extrusion process are obtained. It is noted that the values of the torque and force increase until the free space of the press chamber is filled with metal, reaching maxima of 12.26 kN m and 1.54 MN, respectively. As a result of an analysis of the stress-strain state of metal in the deformation zone, the fields of distribution of equivalent strain, strain rate intensity, and average stresses are obtained and the graph of change in the metal temperature with the time of the extrusion process is plotted. The maximum of the equivalent strain and compressive stresses are observed in the region of contact between the workpiece and the abutment of the press container. That is also where the most intense deformation-induced heating of the metal occurs. A comparison of the results of modeling and microstructural studies indicates that a significant part of work on refining the cast structure takes place at the entrance to the deformation zone and in the abutment region, where the level of compressive stresses is the highest. Plastic deformation of the metal passing through the die leads to the formation of an oriented crystal structure with a grain size of 25 to 30 µm. The results of measuring the hardness of the samples are very consistent with the results of analyzing the structure in the studied regions of the deformation zone. When the workpiece passes through the abutment region of the press container, deformation-induced heating occurs, which leads to a decrease in the hardness from 93 to 67 HV. After the metal passes through the die, recrystallization processes continue in it, leading to a slight increase in grain size and, accordingly, a decrease in the hardness from 79 to 74 HV, which lasts until the bus comes into contact with a cooling medium.

Aluminum alloys have always been the material of choice for the aircraft industry owing to their versatile attributes, such as excellent strength to weight ratio, good corrosion resistance, thermal conductivity, and low production cost after wood. However, these days composite materials, carbon fiber reinforced plastic and fiber metal laminate are substituting aluminum alloys mainly because of their incapability to work at high temperatures. Nonetheless, continuous research in these aluminum alloys will effectively combat with those modern polymer composites and carbon fiber reinforced plastic. And so forth, mechanical and tribological properties of aluminum alloys can nowadays be enhanced by adding a suitable reinforcement in an appropriate volume fraction. Reinforcements like micro or nano sized SiC, Al2O3, TiC, B4C, SiO2 and iron powder when used, can alter the microstructural characteristics that develop excellent physical and mechanical properties in aluminum alloys, primarily for aerospace applications. These alloys are being used in different aircraft components that have a relative motion, like actuators and track roll units of a control surface. Stress and wear are generated due to the relative motion of these components during take-off and landing, causing a rise in temperature. And hence, a brief study on moving components used in aircrafts and tribological behaviour of aircraft components is presented in the literature. Also considering that the selection of an appropriate material for the proper functioning of an aircraft component is critical, three most important properties viz. strength, fatigue and corrosion resistance of an aircraft have been provided. Therefore this review article emphasizes on the following topics: (1) aluminum alloys in the aerospace industries, (2) aircraft components with relative motion, their working and material being used, (3) substantial properties of aircraft components viz. strength, fatigue resistance and corrosion resistance, (4) tribological aspect of an aircraft, (5) elevated-temperature behaviour of aluminum alloys, and (6) role of reinforcement for improving properties. This review article is beneficial for those researchers and academicians who want to seek the understanding, pertaining to the usefulness of the aluminum in the aircraft industry.

Experimental studies have been carried out with theoretical calculations of wave synthesis in the Ni–Al–Cu system using a mathematical model. Approximate analytical formulas are obtained for synthesis performance evaluation. The inverse problem method was used to get kinetic constants that determine process dynamics based on the experimental data and analytical relationships. It is shown that the combustion front propagation velocity increases monotonically with an increase in the reaction sample relative density in the range of relative density values of 0.4 to 0.6. The depth of copper-melt penetration from the center of the sample into the nickel–aluminum matrix depends on the relative density of the sample and diameter of the copper wire: higher densities and larger diameters lead to an increase in the liquid-phase impregnation area. The rate of nickel and aluminum powder frame wetting with copper melt is limited by the synthesis wave speed. Based on the experimental data and analytical ratios, we estimate the effective kinetic constants describing the high-temperature synthesis of the Ni + Al reaction mixture in the presence of copper additives. The thermal effect of the NiAl intermetallic formation reaction and the preexponential factor in the chemical transformation equation are calculated, the exponent value in the ratio for the mixture thermal conductivity is established, and a constant determining the process of nickel–aluminum matrix impregnation with copper melt is found. The macroscopic approach used to analyze the NiAl intermetallic synthesis makes it possible to determine all the desired physicochemical characteristics and model parameters. The mathematical model is suitable for predictive estimates and experimental data analysis in the macroscopic approximation. Approximate analytical formulas are obtained for calculating the NiAl intermetallic synthesis characteristics. They allow for calculating the through channel characteristics and can be used in the design of NiAl products.

With China’s bauxite resources depleting year by year, high-alumina fly ash has been regarded as a potential secondary aluminum resource, with alumina content as high as 40–60%. In view of recognized problems, such as large amounts of circulating acid and environmental pollution in the process of extracting alumina from high-alumina fly ash, Northeastern University has proposed a new electrotransformation method. This method has the main advantages of slag reduction, no waste acid, no waste alkali, and recycling. In this study, the effects of diffusion were examined during electrotransformation, in terms of electrode spacing and concentration difference on solution pH and temperature. In addition, the phase, FT-IR results, roasting weight loss rate of products, D(50), D(90), isothermal adsorption and desorption curves, BET surface area, pore volume, impurity chlorine content of roasted products, and Al recovery rate were investigated. The results showed that pH and temperature increased with prolonged electrotransformation time. And that these products were all amorphous containing-carbon aluminum salt precipitation. Roasted products were all alumina (Al2O3) with a steep broad X-ray diffraction peak. The effects of electrode spacing and concentration difference on isothermal adsorption and desorption curves, BET surface area, and pore volume were not clear. With decreased electrode spacing, the Al recovery rate increased and impurity chlorine content decreased. With increased concentration difference, the Al recovery rate tended to first decrease and then increase, while the impurity chlorine content increased. In other words, small electrode spacing and high concentration difference were beneficial for improving the Al recovery rate.

The phase transformation behavior of lead and zinc in the high-lead slag reduction process was reported in this article. First, the occurrence state of lead and zinc in the slag and the phase transformation behavior of lead and zinc during reduction were investigated. Following, the thermodynamic modeling calculation for the reduction process was constructed and discussed. The results indicated that the zinc in the high-lead slag mainly existed in the form of zinc ferrite and silicate while the lead mainly existed in a silicate form. The XRD patterns of the reduced slag at different coal ratios demonstrated that the lead existing in the high-lead slag in a silicate form could be reduced into the metal phase while the zinc existing in the high-lead slag in the form of zinc ferrite (ZnFe2O4) could be converted into zinc silicate (Zn2SiO4), as the coal ratio increased. The thermodynamic modeling calculation results showed an agreement with the experiment analysis.

A variant of a rheological model of hot deformation is proposed: the law of hyperbolic sine, which, as opposed to standard law, accounts not only for the rate of deformation and temperature of the process, but also the degree of deformation. The material constants in the law of hyperbolic sine are substituted with polynomial functions of the degree of deformation; its coefficients are calculated using a specially developed procedure. The proposed rheological model has been applied for aluminum lithium alloys of lower density, grade 1424, Al–Mg–Li–Zn system, and grade V-1461, system Al–Cu–Li–Zn, for which, using physical simulation at the Gleeble-3800 facility, the flow curves were determined in the temperature range of 400–480°C and the rates of deformation of 1–60 s–1 to the degree of deformation of 0.6. In addition, the influence of the initial state of the material is studied: samples are taken both from the ingot and from hot rolled plates. The constants of the rheological model of hot deformation, including the Zener–Hollomon parameter and the law of hyperbolic sine for the overall range of stresses and deformations, are determined. After approximating the parameters of this model as a function of real deformations using the polynomial law of the 4th order, the rheological model was developed describing the behavior of an alloy in the considered range of temperatures and rates. The parameters of the law of hyperbolic sine are determined as a function of degree of deformation. It is demonstrated that the parameters for a cast material are higher than for a rolled material. A comparison of the standard model with the proposed one demonstrated that the use of a standard model gives overestimated flow stresses in the entire deformation range (up to 12%).

A comparative simulation of hot radial shear rolling (RSR) of billets made of a superelastic Ti–Zr–Nb and a commercial VT6 alloy was performed using the QForm finite element modeling program. Rolling in 48 modes with a variable feed angle and elongation ratio at 4 levels and initial rolling temperature at 3 levels was investigated for each alloy. The Ti–Zr–Nb alloy rheology during hot deformation was determined experimentally by hot upset forging and imported into the QForm program. The presence of maxima on the flow curves at the initial stage of deformation, which are absent in the VT6 alloy, is revealed. Simulation results are presented in the form of fields of the stiffness coefficient, strain rate intensity, cumulative strain degree in the maximum reduction section depending on the rolling mode. General regularities of the Ti–Zr–Nb and VT6 behavior in RSR are similar. The gradient of the fields studied decreases, and the roll pressure and torque increase with an increase in the feed angle and elongation ratio. The initial rolling temperature does not significantly affect the deformation pattern, but it significantly affects the roll pressure and torque. At the same time, the experimental alloy demonstrated the greater tendency to localize deforming forces in the near-contact zone and to increase the gradient of stress-strain state parameters over the billet section. The study of the tightening shape and depth of rolled billet ends showed that the Ti–Zr–Nb alloy has a 3.5–9.6% greater tightening depth. It is shown that experimental alloy rolling requires 1.6–2.4 times higher roll pressure and torque as compared to the commercial alloy.

The 7075 aluminum alloy was subjected to deep cryogenic treatment (DCT) at –196°C with liquid nitrogen for different hours. The wear and corrosion behaviors of the alloy were investigated by hardness, friction and wear, intergranular corrosion (IGC), and electrochemical corrosion tests. The microstructure of the alloy was observed by transmission electron microscope (TEM). The results showed that both the wear and corrosion resistance of the alloy treated with DCT could be improved. After the DCT 12 h, the matrix precipitates of the alloy were fine and homogeneously distributed, and the grain boundary precipitates of the alloy were discontinued, so that the alloy performed better comprehensive properties.

A novel process for the extraction of vanadium and preparation of sodium vanadate from V–Cr-bearing reducing slag is proposed. This process involves several steps of washing, alkaline leaching, evaporation crystallization and cooling crystallization. The washing procedure ensures that chloride and sulfate ions can be mostly washed away from V–Cr-bearing reducing slag. Subsequently, vanadium can be extracted by alkaline leaching, the leaching rate of vanadium can reach 98%. During this process, vanadium enters the leaching solution, and chromium continues to accumulate in the leaching residue. Finally, most of Na2SO4 can be removed from the alkaline leaching solution by evaporation crystallization, then the Na3VO4·12H2O can be prepared by cooling crystallization. The filtrate of cooling crystallization can be recycled as the new leaching medium with some new alkali added, which greatly reduces the discharge of alkaline wastewater and makes the whole process more environmentally friendly.

The technological process of hot-die forging billets for the piston of an internal combustion engine (ICE) of an unmanned aerial vehicle (UAV) made of AK4-1 aluminum alloy using the Deform-3D software package has been modeled. The object of simulation is a real ICE piston mounted on a Russian UAV. During modeling, the following parameters are introduced: the temperature of the tooling and the billet is 450°C, the ambient temperature is 20°C, the speed of the punch is taken as 5 mm/s, and the Siebel friction index is 0.4. A rigid plastic medium is chosen as the material model. The number of elements (6000) is assigned so that at least three of them fit in the narrowest section of the part. Thus, using the example of a stamped piston forging, it is shown that, using computer simulation in the Deform-3D program, it is possible to develop processes of hot-die forging of aluminum alloy billet for the manufacture of pistons for UAV ICEs. At the same time, computer modeling allows you to design a tool, evaluate the power parameters of the hot-die forging process, study the nature of the shape of the billet during die forging, and make the necessary adjustments to the virtual technological process that will make it possible to select the most optimal technical solutions when designing a real process. This computer-simulation technique can be extended to other stamped forgings from aluminum alloys.

An intermetallic alloy based on the Heusler phase—Cu2TiAl—has been obtained by self-propagating high-temperature synthesis (SHS) in the Cu–Ti–Al system for the first time. The modes of frontal combustion of the green mixtures and the processes of phase formation during synthesis have been studied. The resulting products have been studied by X-ray analysis (including high-temperature diffractometry with step heating up to 900 K), scanning electron microscopy, and differential thermal analysis (DTA), and some physical properties have been studied. Electrophysical and magnetic measurements are also carried out for the alloy. The results of X-ray analysis and scanning electron microscopy using energy-dispersive analysis (EDA) have shown that the content of the Heusler phase in the synthesized product is at least 82%. The product also contains copper (CunineAl4) and titanium (Ti3Al2) aluminides. The temperature dependence of the electrical resistivity of the synthesized product is measured for a wide temperature range of 90–1000 K. The resistivity at T = 300 K is 0.3 μm Ωm. The metallic type of conductivity for obtained samples and the anomalous behavior of the temperature curve of electrical resistance in the region of 770–790 K are revealed. Thermal analysis is used to measure the melting point of the synthesized product and reveal additional heat effects at 788, 848, and 1248 K associated with possible phase transitions in the Cu2TiAl intermetallic compound. One possible mechanism of these phase transitions is considered in accordance with the phase diagram of the Cu–Ti–Al system. Magnetic measurement results show that intermetallic samples of the compound obtained by the SHS method exhibit weak ferromagnetic properties with residual magnetization of 0.069 A m2/kg.

Powder metallurgy was used in this study. High purity cobalt and titanium powders were added to copper powders at a ratio of 5–10–15 wt %. The reinforcing powders added to the copper powders were mixed for about 6 hours in a Turbula device. Then, the powders were compressed by applying 600 MPa using a hydraulic press. The samples were sintered at 1000°C for 30 min. After sintering, density measurements, and microstructure and mechanical tests of the samples were done. Scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction analyses were performed in the microstructure characterization. Tensile and wear analyses were performed for mechanical experiments. The tensile test results were determined by applying certain loads to the samples. The tensile strength of the 5 wt % Co–Ti reinforced sample was the highest, with an average of 118.65 MPa, and the ductility increased in parallel. Weight loss, friction coefficient change, and wear diameter image results were obtained from the wear test. The lowest weight loss was observed in the composite containing 5 wt % Co–Ti and this value was determined as 0.0191 g. The increase in the reinforcement rate contributed positively to tensile and abrasion resistance.

Current trends in the application of rare-earth metals (REMs) in two major scientific and technological fields—the production of magnetic and luminescent materials—are considered. It is shown that it is REMs that endow these products with unique properties. The information on the content of the matrix and doping components and their influence on achieving the required characteristics of the most popular magnetic materials is systematized. The potential of new combinations of REMs for further progress in the production of magnetic materials for various purposes is described. Along with the traditional cobalt–samarium and neodymium–iron–boron compositions, new magnetic materials with increased hysteresis properties and better time–temperature stability are developed, and phases with variable valence, used as memory elements in information systems, are synthesized. In addition, the article also reviews and summarizes the results of studies in the creation of luminescent materials, which is another important area of application of REMs. Phosphors based on compounds of REMs are used in the production of high-pressure mercury lamps with improved characteristics, X-ray screens, high- and low-pressure fluorescent lamps, and screens for electrooptical converters. Narrow-band phosphors based on REM compounds are of interest for lamps used for growing plants, especially in areas with a cold climate, where growing plants year-round is possible only with the use of additional radiation sources. The trends in the synthesis of luminescent materials with varied REMs and their combinations are revealed. Emphasis is placed on the need to use chemically pure REM precursors in the synthesis of such materials. The prospects for the creation of nanophosphors, as well as the improvement of methods of synthesis and diagnostic techniques, are noted.

The influence of electromechanical surface treatment (EMT) and nonabrasive ultrasonic finishing (NAUF) on the titanium alloy and the complex influence of the above treatment methods and subsequent aging on the fatigue life and the change in the surface microhardness is studied. Specimens for research are made of rods manufactured of the transition VT22 alloy after the standard thermomechanical treatment. The EMT is conducted by rolling the surface of the specimen with a roller pressed to it and passing a high-density current between them. As a result, the surface thermomechanical treatment is conducted under fast local heating and cooling of the surface. The NAUF is performed by shock treatment with a striking ultrasonic emitter on the treated surface. The rotational bending loading of specimens at stress amplitude of 0.5σu upon the NAUF results in an increase in fatigue life by a factor of 1.8 in comparison with the untreated initial state, accompanied by a slight increase in the microhardness of up to 16%. The EMT reduces microhardness by almost 20% and fatigue life by 70%. The combined processing by EMT + NAUF insignificantly affects microhardness, but increases the life by 40% compared with the EMT. Aging at a temperature of 450°C for 5 h increases the microhardness upon the EMT by 30–40% with a simultaneous twofold increase in durability. The aging of the specimens subjected to EMT + NAUF practically does not increase microhardness, but it increases durability by almost three times compared with the EMT. A fractographic analysis of the fracture surface has shown that the reduction in the life after EMT is associated with a reduction in the stage of crack initiation, which virtually excludes this stage of accumulation of fatigue damage from the overall durability of the specimen.

This paper provides the results of simulating the hot die forging of porous powder preforms with active friction forces applied along the lateral surface of the blank under deformation due to internal cohesion in the die–material system. The study covers the evolution of the distribution of the relative density over the blank cross section at different stages of deformation, the stress-strain state, and the total strain force while varying the boundary loading conditions by changing the initial compression force applied to elastic elements that prevent the die from displacement. It is shown that the active friction forces that act on the periphery of the forged piece adjacent to the die inner side result in areas with a significantly higher deformation intensity compared to deformations in the center of the blank volume. In this case, the volume of the high deformation intensity area and the maximum values of deformation increase with a decrease in the initial compression force of the springs and, accordingly, with an increase in the die displacement value during the deformation. The automatic displacement of the die due to the internal cohesion in the die–deformed material system leads to a decrease in the total deformation force, and the deformation force increases with a decrease in the die displacement value during deformation.

This paper provides the first part of a study on the effect of magnesium on the structural phase composition and physical and mechanical properties of nanostructured aluminum–magnesium composite materials with the composition AlxMgy + 0.3 wt % C60 fullerene. Composite powders are obtained by the simultaneous mechanical activation of the initial materials in a planetary ball mill in an argon atmosphere. It is found that the powders have a complex hierarchical structure made up of 50–200 μm aggregates consisting of 5–10 μm strong high-density agglomerates, which in turn are a combination of nanoscale (30–60 nm) crystallites. It is found that the increase in magnesium concentration in the composite up to 18 wt % makes it possible to obtain crystallites with an average size of less than 30 nm during mechanical activation, while the size of aggregates is less than 50 μm. The maximum solubility of magnesium in aluminum with a crystallite size of 30–70 nm during mechanical activation is 15 wt % (17 at %). Using the differential scanning calorimetry method, it is found that nanostructured composites undergo irreversible structural phase transformations during heat treatment in a temperature range of 250–400°C: recrystallization, decomposition of the α-solid solution of magnesium in aluminum, and the formation of intermetallic β-(Al3Mg2), γ-(Al12Mg17) and carbide (Al4C3) phases. In addition, the Raman spectra contain peaks that, according to some sources, correspond to covalent compounds of aluminum with C60 fullerene—aluminum–fullerene complexes. The data that have been obtained will be used in further research to determine the parameters for the thermobaric treatment of nanocomposite powder mixtures in order to obtain and test bulk samples.

In this paper we study the possibility of producing a WC–15Co ultrafine-grained hard alloy (HA) from a powder obtained by the electroerosive dispersion (EED) of wastes of a VK15 HA in water. As a result of the EED of the alloy in the oxygen-containing liquid, the carbon concentration in the resulting powder decreases from 5.3 to 2.3%. When the powder is heated to 900°C in a vacuum, the carbon content drops to 0.2% due to the presence of oxygen. The resulting powder includes WC, W2C, and Co phases. The particles have a dendritic structure consisting of newly formed tungsten-containing grains and cobalt interlayers. In this study, the controlled removal of oxygen and the replacement of carbon in the powder were performed under heating in a CO atmosphere to t = 900°C. The processed powder has the required phase composition (WC + Co) and contains 5.3% carbon. The particles retain their spherical shape after carbon replenishment. The WC grains in the particles acquire a lamellar configuration, the space between which is filled with cobalt. The average grain diameter was found to be smaller than that in the initial alloy. As a result of sintering the powder in vacuum at 1390°C, a WC–15Co ultrafine-grained HA is obtained, the average diameter of WC grains in which is 0.44 μm, which is several times smaller than that in the initial alloy (1.8 μm). In this case, most of the grains retain their lamellar shape. Due to the fineness and 15% cobalt content, the resulting alloy has high hardness (1620 HV), fracture toughness (13.2 MPa m1/2), and strength (1920 MPa). In terms of the set of characteristics, this material is not inferior to analogs obtained by other methods.

In this paper we present the results of studies of the effect the state of grain boundaries formed in consolidation of beryllium powders by vacuum hot pressing has on the strength properties of sintered beryllium. The dependences of the morphology, elemental composition, and structure of the dispersed strengthening phase, beryllium oxide, on the content of low-melting impurities at the grain boundaries of sintered beryllium were studied using scanning electron microscopy and X-ray microspectral analysis. A new hypothesis that explains the difference in the morphology and structure of reinforcing particles based on the features of the transition of amorphous beryllium oxide to the crystalline state (devitrification) at grain boundaries of metallic beryllium is proposed. It has been theoretically substantiated and experimentally confirmed that the devitrification mechanism can be homogeneous or heterogeneous, depending on the content and ratio of silicon and aluminum impurities. This difference determines the formation of either finely dispersed high-strength reinforcing particles of beryllium oxide or large and less strong oxide clusters. Changes in the morphology and structure of reinforcing oxide particles at the grain boundaries of metallic beryllium, in turn, affect the dynamics of grain growth in the beryllium microstructure during vacuum hot forming processes and, ultimately, the effect of grain-dispersed hardening of sintered beryllium. The results of testing the mechanical properties of industrial hot-pressed blanks of powders with fineness less than 56 μm to determine the effect of various factors (impurity content, their ratio, and particle size of the initial powders) on the strength properties of hot-pressed beryllium are statistically processed. The adequacy of the regularities is estimated using the coefficients of the approximation accuracy, which confirms the conclusions of the theoretical and experimental analyses of the studied problem. One complex indicator of the initial powder quality which makes it possible to predict the strength properties of hot-pressed beryllium is validated based on the statistical studies. The results substantiate new possibilities for controlling the mechanical properties of sintered beryllium for various purposes.

The results of studying the fine structure, chemical composition, and phase composition of boundaries between components of the Cr3C2–Ti hard alloy containing 40 wt % titanium binder in the state after the explosion compaction, as well as after heat treatment, are presented. The heating temperature of the powder mixture during the shock-wave loading is 730°C and the pressure is 14 GPa, which provides the maximal compaction and consolidation of the powder mixture without sintering. Compact samples are heat-treated at a temperature from 400 to 700°C with holding in the furnace for 1 h with subsequent cooling in calm air. The equilibrium phase composition is calculated by numerical thermodynamic modeling using the Thermo-Calc software complex. The structure and elemental composition are investigated using FEI Quanta 3D and Versa 3D electron microscopes with an integrated system of the focused ion beam for foil preparation, as well as FEI Techai G2 20F and Titan 80-300 transmission electron microscopes with the mode of transmission foil scanning. A Bruker D8 Advance diffractometer is used to perform X-ray phase analysis. It is shown that the formation of strong interphase boundaries during the explosion compaction of mixtures of titanium carbide and chromium carbide powders is accompanied by chemical interaction between components with the formation of near-boundary layers having a total thickness on the order of 90 nm. The continuous monotonic variation in Cr and Ti contents is observed in the limits of the transient layer with an almost invariable carbon concentration. The phase composition of the layers corresponds to the equilibrium one calculated under the shockwave compression pressure of 12 GPa, but it is thermodynamically nonequilibrium under standard conditions. Heating to 400°C leads to the dissolution of near-boundary layers and transition of Cr3C2–Ti hard alloys into the two-phase state. Alternating layers consisting of carbon-depleted chromium carbides (Cr7C3, Cr23C6) and titanium carbide (TiC), formed due to the carbon diffusion from the initial chromium carbide (Cr3C2) to titanium, are formed along interfacial boundaries at a temperature of 700°C.

It is found that when a tungsten anode is electrochemically dissolved in a acidic fluorides of alkali metals (K,Na)H2F3 and hydrogen fluoride at a temperature of t ~ 37°C, the resulting atomic fluorine reacts completely with tungsten to form WF6. The latter dissolves in the melt, forming complex compounds (K,Na)2WF8 and (K,Na)WF7, which is accompanied by an increase in the melting point of the electrolyte. The addition of up to 23 mol % LiF and saturation of the electrolyte by WF6 lowered its melting temperature below 18°C, which, in an electrochemical process at a temperature of 35–40°C and an anode current density of 0.3–0.5 A/cm2, made it possible to obtain simultaneously gaseous WF6 at the anode and H2 at the cathode. During the gas-phase deposition of tungsten, dense layers are formed from the resulting gaseous mixture with a stoichiometric ratio of components at a temperature of 550–600°C, and the resulting HF is captured by an electrolyte and used to produce a mixture of WF6 + H2, ensuring the circulation of reagents and the absence of stored waste. Based on the results, a short fluoride cycle in tungsten technology is presented. It uses two operations: the electrochemical synthesis of a gaseous mixture of WF6 + H2 in an electrolyzer with a filling anode made of fragments of metal tungsten and the reduction of WF6 by hydrogen with capture the resulting HF, allowing one to reduce the chain of technological devices in the cycle by almost 2 times with a significant reduction in production costs. The hardware and technological scheme of the production chain for the environmentally friendly production of tungsten products with a capacity of ~48.5 t/year, which can be replicated and modified to produce the necessary products, is presented.

Aluminide coatings deposited by CVD method on CMSX-4 superalloy, modified by palladium and zirconium or hafnium as well as non-modified and palladium modified ones on pure nickel have been studied using positron annihilation spectroscopy. The positron lifetime values and the positron effective diffusion length in the coatings studied point out trapping of positrons in defects associated with dislocations of high density. Palladium used for modification of the aluminide coatings substitutes nickel in the β-NiAl phase. This gives rise to the increase in the positron lifetime indicating a higher number of open volume defects in the crystal lattice. Additional modification of the aluminide coating on CMSX-4 nickel superalloy with zirconium or hafnium causes only slight changes in the positron lifetime which may be related to the differences in location of precipitates in the coatings.

The results of domestic and foreign investigations into the laser surfacing of coatings containing a strengthening carbide phase, as well as metallographic and tribological investigations of coatings by alloy powders of the Ni–Cr–B–Si system, including the addition of nanodispersed titanium and tungsten carbide particles, are presented. Values of the wear resistance coefficient (Kw) of coatings during abrasive wear testing according to the Brinell–Haworth scheme are determined. The use of Kw makes it possible to determine coefficient C when performing a scratch test of the coatings, which depends on the coating hardness, treatment modes, and addition of solid particles. It is found that the magnitude of C is affected by a series of factors such as the processing speed, input laser power density, base melting depth, and carbide phase presence and content. The larger the melting depth is, the lower the coating wear resistance is, which is associated with mixing the base material and surfaced coating. Introducing tungsten carbide nanoparticles in an amount from 3 to 7% makes it possible to increase the coating wear resistance by a factor of 1.5–2.0 when compared with the surfaced powder coating made of the PR-HKh15SR2 alloy and by a factor of 4.6–7.1 with respect to the base material—steel 40Kh. Microhardness of the initial powder is 6400–6600 MPa and increases with the introduction of carbides into it. For example, microhardness reaches 7620–9160 MPa with a WC content of 7% in the coating. Positive surfacing results are found with the emission power density up to 50 W s/mm2, but its further increase leads to the burnout of alloying elements and dissociation of carbides.

The results of long-term work of the group of authors on the problem of the direct reduction of heavy nonferrous metals directly from sulfide compounds contained in concentrates (lead) and metallurgical products (copper, nickel)—white matte and copper and nickel concentrates—from the separation of a converter matte are summarized. The preparation of materials for the reduction and the reduction process itself include the conversion of metal sulfides into oxygen compounds (oxidizing and sintering roasting) with the reduction of metals with carbon-containing reagents (coal and СО), as well as the reduction of copper and, partly, lead from oxide melts with sulfides. Sulfides conversion and reduction operations are associated with the release of sulfur- and carbon-containing compounds (SO2, SO3, CO, and CO2) and, consequently, with the need to capture and utilize gaseous and solid products. A fundamentally new process of the direct reduction of metals from sulfides using their own sulfide sulfur as a reducing agent is proposed. The reducing process occurs through the possible formation of short-circuited electrode pairs in the 2Mez+–zS–2 system due to the donor–acceptor interactions, primarily π binding. The process can be successful occurrence upon the removal of the products (product) of the electrochemical reaction, in particular, S0. Caustic soda is proposed as a reagent. Using the example of the above production materials, the possibility of reducing the metals is shown at temperatures of 550–700°C with the achievement of their deep extraction (more than 99%). The product of sulfide sulfur oxidation, elemental sulfur, reacts with the melt of caustic soda and accumulates in the form of nonvolatile sodium compounds in it.

The synthesis and sintering of the (AlN)x(SiC)1 – x solid solution have been studied under conditions of self-propagating high-temperature synthesis (SHS) gasostating at high nitrogen gas pressures (up to 110 MPa). The phase formation during the combustion of mixtures of aluminum and silicon carbide with a different amount of Al (from 35 to 60 wt %) is studied. It is shown that the optimal amount of aluminum mixed with silicon carbide to obtain a single-phase solid solution (with the complete conversion of aluminum to aluminum nitride, and also without the dissociation of silicon carbide) is 45–50 wt %. Using a mixture with 55–60 wt % Al leads to excessively high temperatures, which in turn leads to the decomposition of silicon carbide to Si + C elements. The optimal parameters for obtaining dense material in one stage are determined. The measured porosity and density of the samples allow us to establish that, for samples with 50 wt % of the aluminum content, prepressing is essential for the final density. It is found that the additive of 5 wt % yttrium oxide increases the density of the material by almost 10%. A similar effect is also exerted by an increase in the initial gas pressure from 80 to 110 MPa. The maximum density that is achieved is 2.7 g/cm3, which is 83% of the theoretical density. The total volumetric shrinkage of the material is 10% ± 0.5, which can be almost completely leveled by the addition of 3 wt % boron. The hardness of the samples reaches up to 2000 kg/mm2.

Self-propagating high-temperature synthesis (SHS) in the Ni–Al–Ti–B system has been carried out. The aim of the study is to obtain, in one process step, a composite material with a ceramic and intermetallic framework and a developed porous structure in combustion mode from the boron–titanium–large nickel-clad aluminum granules powder system pressed by successive batch compaction method. The synthesis process is characterized by a stage nature, in which a highly exothermic reaction between titanium and boron form a boride matrix with developed open porosity and acts as a “chemical furnace” to maintain the reaction in the clad granules, in which nickel aluminides appeared. The aluminide melt impregnates the porous diboride matrix. The synthesis stages are reflected in the thermograms of the process. The final structure of the product has a multiscale porosity, a characteristic feature of which is large round pores (~100–160 μm in diameter) whose location corresponds to the position of clad granules in the initial powder system. Small (0.1–5.0 μm) and some average-sized (up to 15 μm) diboride matrix pores are filled with nickel aluminides. The resulting material has a composite structure of the type of interpenetrating frameworks—ceramic (TiB2) and aluminide (NiAl, Ni3Al). The diboride matrix is ​​formed by chaotically oriented hexagonal small crystals predominantly 0.2–1.0 μm across in size. At the boundaries with macropores, crystal diboride grains increase in size up to 2–6 μm in diameter and 0.5–2.0 μm in thickness, acquiring a more pronounced platelike shape. The main size of intermetallic interlayers filling the pores between the diboride crystal grains is ~0.2–1.0 μm.

A high strain-rate rolling (HSRR) process was successfully used to produce a ZK60 magnesium alloy sheet with a strength-toughness balance. In one-pass rolling, as the rolling rate increases, the edge cracking of the sheets decreases and the grain size increases continuously, and the grain size ranges from 1.4 μm at 5 s–1 to 4.2 μm at 25 s–1. When the strain rate is 5 s–1, the tensile strength and elongation of the ZK60 magnesium alloy are 355 MPa and 12.40%, respectively. As the rolling rate increases, the tensile strength decreases from 355 to 310 MPa. When the rolling rate is less than 20 s–1, the texture strength decreases with the strain rate, from 9.064 at 5 s–1 to 4.480 at 20 s–1, but when the strain rate is 25 s–1, the texture increases to 7.099. At the same time, the study also found that the two-pass rolling process can weaken the texture and increase the tensile strength. The texture strength decreased from 9.04 in a one-pass rolling process to 8.528, and the tensile strength increased from 355 MPa in a one-pass rolling process to 377 MPa.

Microstructure of ceramic coatings formed on commercially pure aluminum by plasma electrolytic oxidation using different amounts of sodium silicate was studied. Analysis of chemical composition and microhardness measurements of the coatings were carried out to characterize the morphology of the coatings. The addition of sodium silicate (1–3 g/L) increased the thickness about 8 orders of magnitude and promotes the growth of the coatings. Chemical analysis of the coatings showed that with increasing sodium silicate concentration in the electrolyte from 1 to 3 g/L, the amount of manganese in the coatings was reduced ∼12%. The contribution of aluminum and silicon changed with a reciprocal relationship. When the concentration of Na2SiO3 changed from 1 to 2 g/L, the aluminium content was reduced about 26% and silicon increased about 80%. When the concentration of Na2SiO3 changed from 2 to 3 g/L, the aluminium content increased about 38% and the concentration of silicon reduced about 60%. The microhardness of the coatings was increased about 2 orders of magnitude by increasing the concentration of sodium silicate from 1 to 3 g/L.

The results of investigations into the organization of the synthesis of silicon carbide fibers in the gas phase using silicon powder, an energy additive of polytetrafluoroethylene (PTFE), and polyethylene (PE) powder by self-propagating high-temperature synthesis (SHS) are presented. Mixtures of the stoichiometric composition are used for experiments. Charge components are mixed in a drum with 3 L in volume with tungsten carbide balls for 30 min. The charge weight is 500 g. Experiments are performed in an SVS-30 industrial reactor. The combustion of the charge of the silicon + PTFE composition is accompanied by a rapid pressure rise from 0.5 to 4.0 MPa for a time shorter than 1 s and relatively rapid pressure drop to 1.5 MPa for 1.5 min. The combustion speed exceeds 50 cm/s. It is established that the combustion is accompanied by the spread of charge components, which is a consequence of the high process speed and intense gas liberation. A cottony light blue material, which consists of silicon carbide fibers 100–500 nm in thickness, is fabricated. The maximal reactor pressure during the combustion of the silicon + PTFE + PE composition reaches 3.1 MPa for 1 s and decreases to 1.5 MPa for 3 min. The combustion speed is about 40 cm/s. The entire accessory volume is filled by cottony blue-gray silicon carbide and SiC powder with equiaxial particles 0.5–3.0 μm in size combined into conglomerates. Silicon needlelike crystals are formed in a transient layer between the powder and silicon carbide fibers. The results of the experiments show the possibility of fabricating silicon carbide nanofibers in relatively large amounts under the combustion of exothermic mixtures.

The optimization of characteristics of pyrolytic chromium carbide coatings (PCCCs) for various fields of industry is discussed. The scope of PCCC application involves the protection of the surface of various details and units made from different materials against corrosion, sticking, high temperatures, and various types of wear. Such versatility of PCCCs is caused in particular by their structural features, which usually represent the superlattice of alternating relatively hard and soft layers, which differ in composition and, accordingly, functional characteristics, such as microhardness or Young modulus. Such a structure at particular periods and layer-thickness ratios corresponds to the maximum figure of merit of the problem of optimal control theory (OCT), which represents the inverse problem stated on the class of solutions of primal problem, which models specific interaction, e.g., abrasive wear. In this case, the primal problem, e.g., indentation description, is an ill-posed inverse problem of mathematical physics, and another optimal strategy is required to solve it. Thus, a hierarchy of optimization algorithms arises and, using it, one can achieve highest functional characteristics of PCCCs. If the primal problem of abrasive wear could not be formalized, a calculation–experimental method developed by the authors, which is also based on OCT, is suggested. The main emphasis is on improving the deposition technology of PCCCs for each specific application using the optimal control theory. In order to obtain a PCCC fulfilling these conditions, it is necessary to consider the physicochemical features of pyrolysis of precursors, as well as the effect of various additives and catalysts on the development of flow process.

The analysis of the influence exerted by the deformation techniques on the conditions of radial-shear rolling (RSR) of commercial purity aluminum A1050 is carried out. Based on finite-element modeling (FEM), the temperature change at various feed angles and elongation in the first and last passes is obtained. The increase in feed angle slightly raises the temperature variations in the surface layer due to the increase in reduction per pass but does not significantly influence total deformation heating during the RSR process. The finishing deformation temperature can be controlled by varying a reduction ratio. In this case, it is necessary to take into account the initial temperature of heating, dimensions of rolled products obtained, and elongation per pass. The dimensions of a workpiece have a significant effect on thermal changes in the RSR process. In the last pass, when the diameters are 20–14 mm, deformation heating is almost completely compensated for by rod cooling upon contact between the environment and the tool and begins to prevail, with an increase in elongation ratio of more than 1.2. An analysis of effective strain (eeff) at various deformation modes shows that the difference in eeff values over the cross section of the rod decreases with an increasing feed angle. A comparison of the data with the hardness and microstructure of the rolled A1050 samples shows that eeff has a significant impact on the change in the structure and properties to a certain value, which is confirmed by the distribution of the microhardness over the cross section of the rods. The mechanical properties of the rods correspond to the properties of commercial purity aluminum in the work-hardened state (σeff ~ 115 MPa, σ0.2 ~ 110 MPa, δ ~ 1%, HV ~ 40–43).

Ta–Zr–Si–B–C–N coatings are obtained by magnetron sputtering in argon, nitrogen, and ethylene atmosphere. The structure of the coatings is analyzed by scanning electron microscopy and energy dispersive and X-ray phase analysis. The mechanical properties of the coatings are determined by nanoindentation. Tribological tests are performed using a Tribometer automated testing machine under a load of 1 N. Wear tracks are analyzed using an optical profile meter. The heat resistance of the coatings is studied at 1000°C. It is established that the coatings obtained in argon are characterized by the highest hardness (30 GPa) and elastic recovery (79%). Moreover, they can be resistant against oxidation up to 1000°C inclusively, which is attributed to the protective film formed on their surface comprised of silicon and tantalum oxides. Reactive coatings obtained in nitrogen are characterized by lower heat resistance in comparison with nonreactive coatings, being completely oxidized by 1000°C. However, they have a low coefficient of friction: less than 0.15.

Using scanning electron microscopy (EDS analysis), magnetic force microscopy, and nanoindentation, a metallographic study of the magnetic structure and nanomechanical properties of sintered rare-earth magnets Nd–Dy–Fe–B of the USC-20L brand has been carried out (Ural Strip Casting Technology). The microstructure of the sintered Nd–Dy–Fe–B magnet of the USC-20L grade includes the following components: grains of the Nd2Fe14B phase are separated by lamellas of the phases enriched in neodymium. Inclusions Nd–29.1% Fe–6.2% C–2.2% O–1.4% Dy are located at the triple junctions of Nd2Fe14B grains. Inclusions Nd–4.5% Fe–9.1% O–6.7% C–4.5% Fe–2% Dy are along grain boundaries containing Nd and Dy oxides. The chemical composition of grains is Fe–25% Nd–6.9% C–1.6% Dy–1.4% B. It is found that, due to irregular grain growth, the interlayers of the enriched Nd phase are connected to each other in the region of grain junctions, causing a concentration of internal stresses and the appearance of a crack. The crack propagates along the grain boundary from one wetted joint of the grains to another, due to mechanical stresses. The phenomenon of intergranular wetting by a phase of Nd-enriched Nd2Fe14B/Nd2Fe14B grain boundaries is observed. It has been established that phases enriched with Nd can pseudo-incompletely (or pseudo-partially) wet such grain boundaries, i.e., form a nonzero contact angle along the grain boundaries and in triple joints. Based on the results of Magnetic Force Microscopy (MFM), a conclusion is made about the presence of a one-dimensional domain structure; domains cross grain boundaries. The presence of pores and inclusions of Nd and Dy oxides localized along grain boundaries is noteworthy. The average transverse domain size of the banded structure is ~1 μm, the energy of the domain wall γ ~ 14 kJ/m2, and the width of the domain wall δ ~ 0.6 × 10–9 m. The nanoindentation method is used to measure the values of nanohardness (H, GPa), elastic modulus (E, GPa), contact stiffness (S, N/m), elastic work (We, nJ) and plastic strain (Wp, nJ) in submicrovolumes of Nd2Fe14B grains. According to the measurement results, the minimum value of Nd2Fe14B grain adhesion Kint = 0.539 MPa m0.5 is estimated.

This study covers the elemental synthesis features of Hf–Ta–B–Ti–Si ceramic materials used to obtain promising high-temperature ceramics and analyze its structure and properties. The macrokinetics of self-propagating high-temperature synthesis (SHS) are studied. Combustion temperature and velocity as a function of initial temperature are plotted. It is established that chemical interactions occurring in the liquid phase play a pivotal role in the combustion process. Structure and phase formation processes are studied using the stopped combustion front technique. The mechanism of phase formation in the combustion wave is determined. The primary crystals of hafnium, titanium, and tantalum diborides are precipitated from the super-saturated melt after the Si and Ti contact melting and B, Hf, and Ta dissolution in the melt through the reactive diffusion process. A two-phase structure consisting of complex solid solutions based on diboride and borosilicide is formed due to the similarity of the crystal lattices. Porous synthesis products of the specified composition are milled into powders with the required particle-size distribution for subsequent hot pressing (HP) or spark plasma sintering (SPS). It is found that specimens produced by HP, SPS, and SHS pressing feature a similar phase composition containing solid solutions based on diboride (Hf,Ti,Ta)B2 and borosilicide (Hf,Ti,Та)5Si3В. Specimens of ceramics produced using the above technologies for physical–mechanical testing are made. It is found that the hardness and elastic modulus of the (Hf,Ti,Ta)B2 solid solution are 2–3 times higher than that of (Hf,Ti,Ta)5Si3B borosilicide. Depending on the composition, the density of the ceramics varies from 8 to 6.5 g/cm3, which corresponds to a porosity of less than 5%. Temperature dependences of heat capacity and diffusivity are determined. The heat conductivity of ceramics produced by HP and SPS is 24.05 and 23.1 W/(m K), respectively.

A new method is proposed for the engineering of SiC-based ceramic-matrix composite materials strengthened by discrete carbon fibers and single-crystal silicon carbide nanowires. Depending on the macrokinetic characteristics of the combustion process, either diffusion layers, particles of silicon carbide, or silicon carbide nanowires with a diameter of 10–50 nm and a length of 15–20 μm can be formed on the surface of carbon fibers. The sequence of chemical transformations and structure formation in the combustion wave of Si–C–C2F4 and Si–C–C2F4–Ta mixtures was studied. Silicon carbide nanowires formed in the combustion wave had high crystallinity and a defect-free TaSi2/SiC interface. The misorientation of the lattices at the interface is about 6%. Nanowires are able to relax the mechanical stresses during growth via the rotation along the growth direction. The optimal combustion temperature for the growth of silicon carbide nanofibers is 1700 K at a ratio of C2F4 : C = 2. The lower temperature threshold for the growth of silicon carbide nanowires is caused by a decrease in the yield of reactive fluorides, while the upper-temperature threshold is caused by a failure of the adsorption blocking mechanism on the surface of the nanofibers and the destabilization of the TaSi2 + Si eutectic droplet. Composites with a SiC–TaSi2 ceramic matrix and a relative density of 98%, a hardness of 19 GPa, a flexural strength of 420 MPa, and fracture toughness of 12.5 MP m1/2 were obtained by hot pressing. An increase in the strength of the carbon fiber-matrix interface has manifested in the suppression of carbon fiber pull-out from the matrix.

In this work, a thermodynamic study of zinc sulfide high temperature oxidative leaching was carried out. At the metals sulfides dissolution under oxidants action in acidic solutions several simultaneously proceeding reactions are possible. With the aim finding the proportion of potential reactions, a thermodynamic calculation was carried out using stoichiometric equations with equal oxidant consumption. Moreover, stoichiometric coefficients were chosen in such a way that reagents could exchange 1 mole of electric charge. Such an approach allows one to ensure a comparison of different oxidants’ usage effectiveness for sulfide leaching. Thermodynamic analysis results are in accordance with experimental data, which confirm that reactions with the formation of sulfur and sulfate-ions are uppermost at zinc sulfide dissolution in sulfuric acid solutions under oxygen action. Oxygen consumption and initial sulfuric acid concentration influence on proportion of this reactions and zinc equilibrium concentration in solution were investigated. Thermodynamic analysis showed that at insufficient acid concentration, which limits the maximum degree of zinc sulfide oxidation reaction advancements with sulfur formation, oxygen is consumed on oxidation reaction with the formation of sulfate-ions, which spend oxygen less effectively, due to four times smaller zinc dissolution. Thermodynamic calculations carried out allowed us to find out optimal proportions of oxygen consumption and initial sulfuric acid concentration, which provide achievement of a maximal zinc equilibrium concentration in solution at a higher effectiveness of oxidant consumption without labor-intensive experiments. At optimal acid consumption, a zinc equilibrium concentration is directly proportional to initial acid concentration. Directly proportional dependence of zinc cations’ formation on acid consumption was also detected at acid concentration optimal values.

To fabricate Cu–Ti composite particles, the method of copper deposition from its sulfate solution on titanium powder particles with the simultaneous mechanical activation (MA) of the mixture in an AGO‑2 planetary ball mill for 5 min is used. The CuSO4 ⋅ 5H2O concentration in solutions is 10 and 16%, which provides molar ratio Cu/Ti = 0.85 and 1.36, respectively, with the complete reduction of copper. The rapid reduction of copper in the form of highly dispersed partially amorphized powder occurs during MA, and composite particles with a thin laminate structure and high reaction ability are formed. Prepared composites are rinsed and stored in argon because reduced copper possesses high activity and rapidly oxidizes in air to oxide Cu2O. After drying, the additional MA of the mixture is performed for 5 min. Pellets 3 mm in diameter and up to 1.5 mm in height are compacted from prepared powders and heated in argon to 700–1200°C. An intense reaction with heat liberation (heat explosion) and the formation of TiCu, Ti2Cu3, and Ti2Cu intermetallic compounds starts upon sample heating. The critical inflammation temperature for composite powders formed by MA with simultaneous copper deposition from the solution is 480°C, which is 400°C below the inflammation temperature of the usual powder mixture of titanium and copper. The alloy has a dendritic structure at a heating temperature close to the melting point, while, if it is exceeded by more than 100°C, the phase distribution in the alloys becomes more uniform and their size decreases.

This article is devoted to the influence of sodium lignosulfonate (SL), anionic surfactants (sodium dodecylsulfate (SDS), sodium dodecylbenzene sulfonate (SDBS)), and their mixtures on the copper cementation rate by zinc. The results demonstrated a copper cementation rate decreasing at LS and SDBS concentrations increasing. Excessive zinc consumption was also detected on copper-ion cementation due to LS and SDBS anion adsorption onto positively charged zinc cathodic areas and copper particles. This led to a decrease in the growth rate of nuclei of copper particles and energy consumption for the formation of new nucleation centers, as well as the creation of conditions for reducing the overvoltage of hydrogen evolution. At the same time, an increase in temperature led to zinc consumption decreasing in the presence of LS. The reagents under investigation could be ranked according to their degree of negative influence on copper cementation increasing in the following order: SDS < SDBS < LS. Testing LS and SDS mixtures showed their irregular influence on the copper cementation rate at different temperatures. In experiments with LS and SDBS mixtures, a linear decrease in the copper-ion cementation rate upon an increase in SDBS concentration and simultaneous zinc-consumption enhancement was fixed. Due to the negative influence of the investigated reagents, we offered a purification method from organic impurities through the use of multilayered alumosilicates modified by cationic surfactants. The results indicate the high effectiveness of removing organic impurities from solutions, which allowed us to increase the cementation rate in the presence of the LS and SDBS mixture by 50% while, at the same time, decreasing zinc consumption. © 2020, Allerton Press, Inc. This work was supported by the Russian Foundation for Basic Research as part of scientific project no. 18-38-00388.

Experiments were conducted on high-energy surface treatment of a structural steel substrate with a flow of tungsten, nickel, and titanium nitride powder particles. The impact pressure of the steel target and particles accelerated by explosion energy was estimated using the momentum conservation equation and the linear equation of the particle material shock adiabat. It was found that the impact pressure of the target and particles is 62 GPa for a tungsten particle, 48 GPa for a nickel particle, and 41 GPa for a titanium nitride particle. The heating temperature of particles during their collision with the steel target surface was calculated taking into account the conditions of mass and momentum conservation at the shock wave front. The maximum heating temperature of particles at the point of their collision with the substrate surface (at a particle velocity of 2000 m/s) is 1103 K for tungsten particles, 755 K for nickel particles, and 589 K for titanium nitride particles. It was shown that the steel target strength increases when it is subjected to high-energy treatment with a flow of particles. The maximum hardening of the steel target surface layer increases by 32–55 % compared to initial microhardness and is observed at a depth of 2–4 mm from the treatment surface. Then it decreases to the value of starting material microhardness (170 HV) at a distance of 15–20 mm from the treated surface.

Gold cementation kinetic features from cyanide solutions using zinc powders of various origins were studied. The first powder was obtained by distillation and is currently used in the vast majority of industries (traditional powder). The second powder was obtained by electrochemical reduction from alkaline solution (electrolytic powder). The main distinguishing feature of these powders is specific surface area. This indicator for the electrolytic powder is 2.6 times higher than for the traditional one (3.02 and 1.16 m2/g, respectively), which is associated with dendritic form of electrolytic powder. For cementation studies, a solution with a gold content of 50.8 μmol/dm3 and 0.04 mol/dm3 sodium cyanide (NaCN) was taken. Studies have shown the presence of a depassivation period associated with oxide film dissolution on the powder surface and overcoming diffusion difficulties. The depassivation period of a traditional powder (10–15 seconds) exceeds the depassivation period of an electrolytic powder (5–8 seconds). Values of cementation reaction experimental rate constants are determined for the process using traditional and electrolytic powders at different ratios of zinc and gold masses in solution. Experimental reaction rate constants for electrolytic powder under the studied conditions are 1.3–1.6 times higher than the experimental rate constants for traditional powder. Zinc oxidation rates are compared under these conditions for various ratios m(Zn)/m(Au). Powder dissolution rates referred to specific surface area (taken in initial period) practically do not differ. The electrolytic powder’s absolute dissolution rate at the initial time is almost two times greater. As powder reacts with an alkaline solution, absolute dissolution rates of electrolytic and traditional powders are equalized.

This work is devoted to the preparation of powders of Ti2AlC and Ti3AlC2 MAX phases by self-propagating high-temperature synthesis (SHS) using the magnesium-thermal reduction from oxide feedstock. Oxide TiO2 is used as the titanium source, and magnesium is used as the reducing agent. Purification with the removal of magnesium oxide is performed in diluted hydrochloric acid at a temperature of 70°C and concentration of 1 : 3. The target product yield with the magnesium-thermal reduction is 35–40%. It is revealed that the synthesis product with the stoichiometric component ratio after chemical leaching in hydrochloric acid consists of Ti2AlC, MgAl2O4, and TiC. The formation of spinel MgAl2O4 is associated with the deficiency of the magnesium reducing agent in the charge; herewith, aluminum partially enters the reduction reaction of titanium from its oxide with the formation of Al2O3. This leads to the formation of spinel MgO ⋅ Al2O3. An increase in the content of excess magnesium in the charge from 20 to 30 wt % conditions the complete reduction of titanium from its oxide by magnesium with the formation of the Ti2AlC MAX phase and titanium carbide. A decrease of 10 wt % in the carbon content causes a decrease in the titanium carbide fraction to 4%. The product, containing Ti3AlC2 and Ti2AlC MAX phases, as well as TiC, is formed at an excess soot content from 20 to 35%, and the Ti3AlC2 weight fraction increases from 86 to 89%, respectively. These powders comprise agglomerates (87% of them are smaller than 65 μm) consisting of thin plates of MAX phases 70–100 nm in thickness.

A characteristic of obtaining metal powders by direct current electrolysis is changes in the morphology of particles over the loose deposit layer thickness up to the formation of large spherulites. Deposits should be periodically removed from the cathode in order to obtain a powder with homogeneous composition. This paper justifies the choice of the parameter describing the change in loose deposit properties and proposes a method for determining the periodicity of its removal from the cathode. Loose zinc deposits were obtained at 25°C from zincate electrolyte containing 0.3 mol L–1 of ZnO and 4 mol L–1 of NaOH at a current setpoint exceeding six times the limiting diffusion current calculated using the smooth electrode. Electrode potential, deposit thickness and evolved hydrogen volume were measured directly in the process of electrolysis. Current redistribution between the metal reduction and hydrogen evolution leads to a change in the structure of loose deposit particles. It is shown that the differential current efficiency of zinc is the parameter describing the change in the loose zinc deposit density. Its value should not exceed 0.96, in order to ensure deposition of loose deposit with homogeneous properties. A further increase in current efficiency will lead to the formation of aggregates at the deposit growth front. It is proposed to determine the periodicity of loose deposit removal from the cathode using the empirical equation for the time dependency of differential current efficiency of zinc. The mathematical and statistical analysis of the data obtained in six replicates was carried out. The interval approach made it possible to significantly narrow the range of permissible differential current efficiency values and, as a consequence, to determine empirical equation coefficients with acceptable accuracy and calculate the growth time period of a deposit with homogeneous structure. The obtained approach can be used to estimate the time period of loose metal deposition accompanied by hydrogen evolution. © 2020, Allerton Press, Inc. This study was supported by the Government of the Russian Federation, regulation no. 211, state assignment no. 0836-2020-003.

The use of both traditional powdered carbon materials (graphite, soot, charcoal, and shungite) and novel carbon nanomaterials (nanodiamonds, fullerene, nanotubes, and graphene) as a dispersed reinforcing phase in aluminum matrix composites (AMCs) and as reagents for the synthesis of reinforcing particles of titanium carbide (TiC) in AMCs is considered. It is noted that the main direction of AMC development to significantly improve the mechanical properties consists of the transition from micron-sized reinforcing particles to nanoparticles, and that the use of novel carbon nanomaterials could play a decisive role in this case. It is necessary that the technologies for producing such AMCs provide the appropriate parameters of the nanoparticles, their uniform distribution throughout the matrix, and a strong adhesive interfacial bond with the matrix. However, the implementation of these technological requirements is a great problem, since carbon and titanium carbide nanoparticles cannot be wetted by aluminum at a temperature below 1000°C and are prone to the formation of agglomerates from nanoparticles owing to interparticle adhesive forces, the magnitude of which increases to the greatest extent with a decreasing particle size. An overview of the achievements and unresolved issues in the use of powdered carbon forms in different solid-phase and liquid-phase methods for manufacturing AMCs based on various techniques is presented. It is shown that the potentialities of using traditional carbon materials are not still exhausted. Considerable attention is paid to the use of self-propagating high-temperature synthesis (SHS) for obtaining reinforcing titanium carbide particles with the use of different carbon materials to produce AMCs.

This paper investigates the physicochemical characteristics and gas-sensitivity mechanisms of nickel oxide (NiO) and nickel ferrite (NiFe2O4) obtained by levitation-jet synthesis LJS). Properties of synthesized materials were examined using various spectroscopic methods. XPS showed that the presence of Ni3+ ions in samples reduced significantly with an increase in the specific surface area of the powders and a decrease in the average diameter of their particles. In this regard, it can be concluded that the number of uncompensated Ni2+ vacancies in such samples also decreases and the concentration of O2– vacancies, on the contrary, increases significantly. The Raman spectra of nanoscale NiO lacked a magnon band, which is usually observed at v = 1500 cm–1, whereas the spectrum of nanoferrite sample had a pronounced 2M band, which indicates an increase in spin correlation. According to the analysis of UV spectra of the samples, there is an increase in reflectivity values with an increase in wavelength for large nanoparticles when compared to the corresponding values for small particles. In this regard, we suggested that Ni-based oxide nanoparticles are semiconductors with an indirect transition to band-gap energy, and this is in sharp contrast to the data obtained earlier by other researchers. The gas sensitivity of nanoscale powders was investigated in relation to carbon monoxide and nitrogen dioxide at operating temperatures of 350–500°C. An evaluation of the results made it possible to conclude that the operating characteristics of the sensors that we propose are superior in a number of parameters to the similar characteristics of sensors made of commercial powders, as well as of powders obtained by other synthetic methods.

This paper presents an overview of the results of the application of metal-sprayed coatings to protect the outer surface of electric submersible pumps (ESP) from the effects of complicating factors in oil wells. The metal-sprayed coating is applied using hot spraying, and the choice of the method is based on the chemical composition, the materials that are used, and the properties of the finished coating. The most common coatings on the Russian market include monel and austenitic stainless-steel alloys applied by arc metallization or high velocity spraying. Traditional coatings obtained by thermal spraying are characterized by an insufficiently high level of physical, mechanical, and chemical properties. Studies of the abnormal cases of submersible electric motors (SEMs) have shown that the most significant disadvantages of the applied coatings include insufficient resistance to mechanical shock, as well as abrasive wear; higher electrochemical potential in relation to the base metal; violations of the application technology; and significant coating porosity. One of the main reasons for the observed disadvantages is a limited number of traditionally used methods and materials. To solve the problem of using protective SEM coatings and significantly increase their properties, service life, and economic efficiency, it is necessary to use modern scientific achievements in the development of coatings to protect metal surfaces from wear and corrosion, namely, to expand the number of coating methods and materials, work out a methodology for assessing the quality of coatings, and develop a methodology for assessing the economic efficiency of protective coatings. Solving these problems will allow us to make a reasonable technical and economic choice of a specific SEM coating for specific operating conditions.

Comparative investigations of the structural characteristics and functional properties of Ti–Al–Mo–N and Ti–Al–Mo–Ni–N coatings fabricated by the ion-plasma-vacuum-arc deposition (arc-PVD) method are performed to study the influence of nanostructuring nickel additives. Coatings have a multilayered architecture with alternating layers of titanium and molybdenum nitrides. The molybdenum concentration is about 22 at % and that of nickel is 7 at %, which corresponds to optimal amounts for the best strength and tribological properties. It is shown that, when introducing nickel, the coating modulation period decreases from 60 to 30 nm with a simultaneous increase in hardness from 37 to 45 GPa. Herewith, the fracture toughness of coatings, which was judged from the relative work of plastic deformation and parameter H/E and H3/E2, increases. Ductile nickel added to the structure of the hard nitride coating promotes a decrease in the level of compressing macrostresses in the material from –2.25 to –0.58 GPa, which, however, does not lead to a decrease in hardness and wear resistance, as is shown by scratch tests. It is concluded that the factor determining the physicomechanical characteristics of the coating is the refinement of the grain structure of the material rather than the macrostress level. The introduction of nickel positively affects the heat resistance of the coating, which successfully protects the substrate material against the oxidation at temperatures up to 700°C, which can be conditioned by the probability of the formation of Ni-containing oxides NiMoO4 and NiTiO3 on the surface. Herewith, their appearance, fracture, and effect as abrasive particles can be the reason for the variation in the wear mechanism under friction at high temperatures.

Specific features of the morphological and structural characteristics of nanopowder particles fabricated by grinding bulk natural diamond and by detonation synthesis are investigated. It is shown by high-resolution transmission electron microscopy, scanning electron microscopy, and low-angle X-ray scattering that, in contrast with the detonation synthesis nanopowder, which consists of similar in size and isometrically primary particles, natural diamond particles fabricated by grinding have a broader spread in regards to size and a preferentially platelet form. It is established by the X-ray structural phase analysis and Raman spectroscopy used in addition to above-listed methods that the structure of particles of nanodiamond formed from natural diamond is similar to the structure of detonation-synthesis nanodiamond. Each particle of natural nanopowder, similarly to detonation-synthesis nanodiamond, consists of a diamond core having a crystal lattice of the cubic crystal system and a shell containing mainly nondiamond forms of carbon with sp2 hybridization with a complex structure. The data on the evaluation of the average particle size of nanopowders of natural diamond and detonation synthesis by three methods, including BET, show results that satisfactorily agree with each other. Herewith, an average particle size of natural powder nanoparticles is close to 24 nm, while that of detonation-synthesis nanodiamonds of the UDA-S-GO brand produced by FRPC Altai is close to 5.6 nm. An insignificant increase in interatomic distances in diamond nanocrystals is revealed when compared with the bulk diamond crystal. The investigation and analysis of numerous images of natural diamond nanocrystals and detonation synthesis nanocrystals formed by high-resolution transmission electron microscopy show that the dislocations and point defects are most often defects in nanodiamonds.

The topicality and efficiency of applying a silicate-containing inorganic coating as an electric insulator when producing soft magnetic composite materials (SMCMs) from iron powders are substantiated. The influence of the sodium silicate (Na2O–SiO2) concentration in an aqueous solution on the formation kinetics of the dielectric coating on iron powders of various brands is shown as well as on their weight increment, average coating thickness, and physical and manufacturing characteristics. It is established experimentally that the influence of particle morphology of iron powders and surface-tension coefficient at the liquid–solid interface on the coating thickness can be indirectly evaluated by wettability characteristics, in particular, by the contact angle. The peculiarities of formation of interlayer SMCM boundaries are considered. Elemental mapping using an energy-dispersive microanalyzer shows that the coating thickness changes after sample compaction under a pressure of 600 MPa and subsequent heating in a range of 400–600°C, and silicon partially redistributes in the dielectric layer. This is caused by the fact that silicon, having a higher oxygen affinity when compared with iron, actively reacts with oxygen arranged on the surface of iron particles and/or reduces iron oxides, forming SiO2 dioxide in the form of a dense film, which, on the one hand, protects iron particles against oxidation, and on the other hand, the dielectric layer affecting specific magnetic losses is formed in the contact zone of iron particles. It is established that the distinctive feature of densification of iron powders with the coating is the prevalence of the structural deformation under compacting, because the coating reduces the internal friction coefficient. It is shown that the developed SMCM corresponds to modern requirements demanded of soft magnetic composite materials in regards to its magnetic characteristics.