Mechanocomposites used as precursors in high-temperature synthesis increase the possibility of chemical reactions executed in a solid-phase mode: they expand the concentration limits of combustion, change burning temperature and rate, ignition temperature, etc. Issues related to the possibility of changing the mechanocomposite structure at both macro and micro levels canbe important for subsequent obtaining of a synthesis product with a required composition, structure and properties. This paper provides selection of optimal modes for preliminary mechanical activation to obtain precursors for high-temperature synthesis. The main controlling parameters of the activation action on the Ti + Al powder mixture were mechanical activation time and power load intensity. One of the determining factors for choosing the optimal mode of mechanical activation is the formation of maximum possible microstrains without the appearance of mechanical synthesis products at the given grinding parameters. It follows from the analysis of structural parameters that these conditions can be achieved at the mill energy intensity of 20 g within over 13 min of mechanical activation impact, but it is not possible to implement due to powder mixture sticking to grinding media. 7-minute treatment at the intensity of 60 g leads to the beginning of mechanochemical synthesis, which limits the mechanical activation time interval. Thus, it is necessary to select activation modes corresponding to the mechanical activation time of 7 minutes at the ball mill energy intensity of 40 g to ensure subsequent implementation of high-temperature synthesis. The studied morphology of mechanocomposites obtained in this mode demonstrated that a plastic aluminum matrix creates conditions for an ideal contact of reagents, and the material formed can be regarded as an elementary reactor in the volume of which the most favorable conditions for solid-phase diffusion are created.

The article proposes using the agricultural waste of Cashew Nuts Shells (CNS) from the Republic of Côte d’Ivoire to produce activated carbon used in water treatment by physical activation. Washed and crushed CNS was carbonized at 800 °С. The obtained crushed and charred CNS was physically activated with water vapor within the temperature range of 400 to 700 °С. Specific surfaces (SBET) and porous structures of obtained activated carbon samples were investigated by low-temperature nitrogen absorption using X-ray diffraction (phase) analysis. The results showed that an increase in the activation temperature with a fixed activation time leads to larger material specific surface, microporous structure development and higher total volume of mesoand micro pores of activated carbons obtained. The X-ray phase analysis results demonstrated that the degree of graphitization, interlayer spacing and crystallite size change insignificantly. It was shown that CNS can be used for activated carbon production that is not inferior by its sorption properties to analogues currently used for water purification.

The paper presents the results of an ellipsometric study of compacted powders of aluminum-based binary alloys containing 1,5 wt.% of rare earth elements (Sc, La, Ce, Sm) and cast aluminum-silicon alloys with the following compositions: Al–10Si–0,5Mg– 0,3Fe–0,1Ca and Al–12Si–0,6Mg–0,5Fe–0,5Ca–0,45Na. An immersion method was used to determine the optical constants of massive polycrystalline alloys obtained by remelting these powders in vacuum, as well as their oxide films for a wavelength λ = 0,6328 μm. Using the optical constants of these alloys, the dependence of their reflectivity on the surface oxide film thickness was calculated. It was found that an increase in the amount of the alloying component and intermetallic phases in the alloy decreases its reflectivity. In addition, the optical constants were used in the construction of modified Δ–ψ nomograms calculated using the Maxwell-Garnett equation that make it possible to determine the thicknesses of oxide films on particles and the volume fractions of metal in compacted powders, and to study the processes of their oxidation in air. It was shown that oxidation of aluminum ASD-4 powders and Al–1,5% REM binary alloys at 600 °C is described by a simple model where a decrease in the metal fraction leads to an increase in the oxide film thickness. It turned out that the oxidation of aluminum-silicon alloys is much faster and not described by this model, which may be due to the appearance of a liquid phase in the powder. A large number of metal droplets on the surface of particles increase the amount of metal on the studied tablet surface in general. The high oxidation rate of aluminumsilicon alloys in air can be explained by the surface activity of magnesium in relation to liquid aluminum.

The influence of different methods used to produce Fe–Cu alloys from immiscible components was studied. Alloys with limited solubility (LS) or pseudoalloys (PA) in a liquid or solid state have long been impossible to obtain with traditional metallurgy methods. This is why developing low-cost and simple technologies to produce such alloys and materials based on them with a possibility to set the required level of physical and mechanical properties is still a relevant problem. This study uses energy-efficient SHS metallurgy method to produce a pseudoalloy with a composition, wt.%: 70Cu–30Fe from oxide materials for the first time. This technology offers using chemical energy generated in the reaction of highly exothermic thermit compositions (in a combustion mode) making it a very energy-efficient method for cast material production. Short synthesis time (tens of seconds), and top surface of ingots protected from oxidation with an oxide melt (Al2O3) enables synthesis in atmospheric conditions. Rods with the same composition were obtained using single-stage vacuum induction remelting from pure (impurity-free) Fe and Cu components for comparative structural studies of alloy sample components. It was found that high melting temperatures of the SHS alloy provides higher solubility of Cu in Fe. Then, when crystallized, structural components are released in the form of small dispersed particles throughout the volume and form a hierarchical structure typical for the SHS alloy only. 70Cu–30Fe alloys produced in a combustion mode (SHS) have a homogeneous structure with structural components distributed uniformly throughout the sample volume, which can be of great practical interest, in particular, for making isotropic and anisotropic hard-magnetic materials with high magnetic energy.

A cast material based on the Nb2AlC MAX phase was obtained by SHS metallurgy. Synthesis was carried out from the Nb2O5– Al–C mixture with a high-energy CaO2–Al additive. Thermodynamic calculation results correlate well with experimental data. It was found that the CaO2–Al additive content has a substantial effect on the thermodynamic parameters and phase composition of the final product. It was shown that synthesis from the specified mixtures passed in a stationary mode with steady combustion wave. Increasing the additive content leads to increasing combustion rate (from 6 to 12 mm/s), and product yield to ingot increases (from 30 to 47 %) up to 15 wt.% of the additive and then decreases. Variation in the composition of initial mixtures can provide a significant impact on both synthesis parameters and final product phase composition. Optimal conditions of material synthesis to ensure maximum yield of the Nb2AlC MAX phase in the ingot composition were determined. The liquid phase lifetime during synthesis is a determining factor influencing the Nb2AlC content in the final product. It is shown that the maximum Nb2AlC phase amount (67 wt.%) is reached with 15 wt.% of the high-energy additive in the initial charge.

The paper provides the results of an experimental study into the properties of compressed and sintered compacts of the following powders: VT-22 high-strength titanium alloy manufactured by plasma spraying of industrial titanium production waste, PTM-1 grade titanium manufactured by the hydrate-calcium method, and PV-N70Yu30 nickel-aluminum alloy. It was shown that charge composition selection for composite blank manufacturing is connected with the need to ensure optimization of several competing target functions. The relative density and strength of compacts under axial compression after sintering, as well as charge cost were chosen as optimization criteria. The problem was set and the method was proposed to select an optimal charge composition providing the necessary values of density, strength, as well as relatively low cost of products. The problem of multi-criteria optimization was solved based on the ≪ideal point≫ method. The results of calculations were compared with the previously obtained solutions of the problem under consideration using the Pareto method, linear programming, and generalized criterion. It was shown that different methods of multi-criteria optimization lead to significantly different results. In this case, the ≪ideal point≫ method gives the minimum discrepancy between the experimental and model values of the optimization criteria selected. The results of this study were used to create an expert system for the multi-criteria optimization of composite manufacturing processes. The charge composition obtained by the «ideal point» method was transferred to an industrial plant where an axially symmetric part was manufactured. The ultimate strength and relative density of the manufactured part material were in conformity with the predicted values.

The article focuses on the preparation of amorphous coatings on the Steel 1035 surface by electric spark treat the coating composition control by changing the granule mixture composition was studied. EDS analysis showed that the coatings obtained contain W, Mo, Co and Ni in different ratios. The weight of granules having different compositions decreased by 11–16 wt.% in 6 hours of treatment as a result of electric erosion. The mass transfer coefficient varied from 33 to 54 %. X-ray diffraction analysis showed the predominance of the amorphous phase in the composition of layers deposited. Annealing of the coatings at 1150 °C led to amorphous phase crystallization into M23(C,B)6 type borocarbide and α-Fe. The coatings had an increased microhardness of 10–15 GPa, and their wear resistance under dry sliding wear conditions at 10 and 50 N loads was 3,3 and 1,6 times higher, respectively, than in Steel 1035. The highest values at both loads were shown by samples without nickel, while samples without tungsten featured the lowest values. The coatings had a friction coefficient within 0,27–0,31 that is lower than for Steel 1035 by 13–30 %. Wear resistance of the coatings under dry abrasive wear conditions at the 25 N load was 3 to 5 times higher as compared to uncoated Steel 1035. Samples without nickel demonstrated the best performance, while samples without cobalt had the worst indicators. Thus, it was shown that tungsten and cobalt increase wear resistance of iron-based amorphous alloys, while nickel and molybdenum tend to worsen their tribotechnical behavior.

Ni–Al intermetallics have high heat resistance and therefore they are used as coatings for steel parts running under high temperature conditions. A method for liquid-phase aluminizing of preliminary nickel-plated steel samples followed by diffusion annealing was offered to form such coatings. Liquid-phase aluminizing can form the second aluminum layer on the nickel-plated steel and diffusion annealing provides formation of a coating based on Ni–Al intermetallics. Diffusion annealing (t = 650÷850 °C, τ = 1, 2 and 5 hours) was done at samples coated with aluminum at 750 °С. It was found that the technology offered ensures forming surface intermetallic layers with a thickness depending on the temperature and time of annealing. Annealing at 650÷800 °С during 1÷5 hours provides forming mainly up to 50–140 μm thick Ni2Al3 layer, while NiAl and Ni3Al layers featuring the highest heat resistance are formed at 850 °С during 5 hours. The heat resistance of these coatings showed that due to refractory NiAl layer formation on the surface, the sample resists to failure at a testing temperature of 750 °С during 300 hours.

April 10–12, 2019, Minsk, Belarus