The article considers a brief review of the foreign publications on the study of the structure, phase composition and properties of five-component high-entropy alloys (HEAs) in different structural states in a wide temperature range over the past two decades. HEAs attract the attention of scientists with their unique and unusual properties. The difficulties of comparative analysis and generalization of data are noted due to different methods of obtaining HEAs, modes of mechanical tests for uniaxial compression and tension, sizes and shapes of the samples, types of thermal treatments, and phase composition (bcc and fcc crystal lattices). It is noted that the HEA with a bcc lattice has mainly high strength and low plasticity, and the HEA  with a fcc lattice has low strength and increased plasticity. A significant increase in the properties of the FeMnCoCrNi HEA with a fcc lattice can be achieved by alloying with boron and optimizing the parameters of thermal mechanical treatment at alloying with carbon in the amount of 1 % (at.). The deformation curves analyzed in the temperature range –196 ÷ 800 °C indicate an increase in the yield strength with a decrease in the grain size from 150 to 5 microns. As the temperature decreases, the yield strength and elongation increase. The effect of deformation rate on the mechanical properties is an increase in the ultimate strength and yield strength, which is most noticeable at high rates of 10^–2 ÷ 10³ s^–1. The features of HEAs deformation behavior in the mono- and poly-crystalline states are noted. The complex of high operational properties of HEAs makes it possible to use them in various industries. There are good prospects of using energy treatment to modify the surface layers and further improve HEAs properties.

The paper presents the results of complex studies of the structure, microhardness and depth of the hardened surface layer of 40Kh steel formed as a result of electromechanical treatment with dynamic application of a deforming force (EMT with impact). The research was carried out using optical microscopy, X-ray diffraction analysis, and microhardness methods. The method of electromechanical treatment with dynamic force impact consisted in simultaneous transmission of electric current pulses and deforming force through the contact zone of the tool with the part. As a result of shock-thermal effects with different current densities (j = 100 A/mm²; 300 A/mm²; 600 A/mm²), segments of the hardened layer of different sizes and structure composition are formed on the steel surface in cross-section. Analysis of structural and phase transformations in the surface layer of 40Kh steel subjected to dynamic electromechanical treatment indicates the formation of a specific structure of the white layer, the structure and properties close to the amorphous state of the metal with a maximum hardness HV = 8.0 – 8.5 GPa. As you move away from the surface, a transition zone is formed behind the segment of the white layer with a structure that does not have the characteristic needle structure of martensite. It was found that with an increase in the current density during shock electromechanical treatment, the depth of hardening increases by 4 – 5 times with a simultaneous increase in the heterogeneity of strength properties; the level of micro-stresses increases by 25 %. Experimental data on the structural state, microhardness and depth of the surface layer of 40Kh steel show that electromechanical treatment with dynamic (shock) application of the deforming force causes deeper transformations in the steel structure compared to traditional static EMT. The results obtained show that as a result of electro-mechanical processing with impact, the intensity of the temperature-force effect on the steel surface layer increases, which allows you to open the internal reserves of 40Kh steel and control the process of forming its structure and phase states.

An isothermal diagram of decomposition of supercooled austenite of R350LHT steel was constructed based on the results of dilatometric, metallographic and hardness analysis of this decomposition during continuous cooling and under isothermal conditions. When comparing the thermokinetic and isothermal diagrams, it was found that the thermokinetic diagram plotted during continuous cooling shifts downward and to the right in comparison with the isothermal diagram. This result is fully consistent with the known regularities. During the research, the critical points of R350LHT steel were determined: Ас₁ = 711 °С; М_n = 196 °С. This isothermal diagram was used to determine the temperature of the minimum stability of overcooled austenite, which was 500 °C. Under isothermal conditions, pearlite-type structures appear in the temperature range from 700 to 600 °C. At 550 °C, a mixture of pearlitic and bainitic structures is formed. In the temperature range from 500 to 250 °C, bainitic structures are formed: at 500 – 400 °C – upper bainite; at 350 ° C – a mixture of upper and lower bainite; at 300 – 250 °С – lower bainite. Almost in the entire studied temperature range of overcooled austenite isothermal decomposition, an increase in the hardness of the transformation products is observed with a decrease in the holding temperature from 246 HV (at 700 °C) to 689 HV (at 250 °C). However, at a temperature of 500 °C, a slight drop in hardness occurs, which is apparently caused by the appearance of retained austenite during the development of bainitic transformation.

The article presents the results of theoretical and experimental studies of leaching of polymetallic manganese-containing and ferromanganese ore. Thermodynamic calculations and experimental studies on enrichment of manganese-containing raw materials made it possible to determine the main technological parameters of the extraction of manganese, iron and non-ferrous metals, and to develop technological schemes for enrichment of various types of manganese-containing raw materials. The studies were carried out for polymetallic and ferromanganese ores of the Kaigadat deposit, the Selezen deposit, the Sugul site, located in the Kemerovo Region – Kuzbass. Before carrying out laboratory studies, the authors have performed thermodynamic analysis of ore leaching, chemical and X-ray structural analyzes of the samples. Laboratory tests were carried out on a multichamber autoclave unit MKA-4-75 using calcium and iron chlorides as solvents. Since the introduction of a reducing agent into the charge during leaching significantly improves the conditions for dissolution of oxides and hydroxides of manganese in calcium chloride, a series of experiments was conducted with the use of charcoal in the charge. Thermodynamic calculations have shown that the leaching process is fully implemented in the temperature range from 323 to 673 K. The results of the experiments confirmed the theoretical research results. The obtained data allowed the authors to propose a technological scheme for hydrometallurgical enrichment of polymetallic and ferromanganese ores to produce high-quality concentrates. All processed products are suitable for use. The use of optimal technological parameters of enrichment allows 95–97 % of manganese, up to 80 % of nickel, up to 99 % of cobalt, and 96–98 % of iron to be extracted from polymetallic manganese-containing raw materials. As a result of the deposition of these elements, high-quality concentrates of manganese, nickel, iron, cobalt are obtained. According to the proposed technological scheme for ferromanganese raw materials with a high content of silicates, it is possible to obtain high-quality concentrates of manganese and iron, while the extraction of manganese is 90–92 %, and of iron – 86–90 %.

The article describes the results of studies on ore dressing waste processing at the enterprises of the Kursk Magnetic Anomaly with production of metals and building materials. About 1.8 billion tons of tailings were stored there. Significant feature of deposits formation is division of tailings by size and specific gravity in water stream, since tailings are transported from the enrichment plant to the tailing dams by hydrotransport. Characteristics of the tailings from wet magnetic research method was applied, including system analysis and scientific generalization, data processing using methods of statistics, probability theory and mathematical modeling. The authors have systematized the results of tailings leaching of following types: agitation leaching in percolator, agitation leaching after activation in disintegrator in the dry state and reagent leaching in disintegrator. Regression analysis of experimental data have been carried out, on the basis of which graphs of dependence of iron extraction on the values of variable process factors were constructed. The used enrichment technologies are limited by extraction limit, which results in processing tailings. The use of these tailings by traditional technologies is not economically efficient, and upgrading of enrichment processes is advisable using hydrometallurgical and chemical technologies. Promising direction in metals extraction from mining waste is combination of processing technologies based on possibilities of both chemical enrichment and activation in disintegrator. It was determined that mechanochemical activation of tailings in disintegrator simultaneously with leaching can significantly increase extraction while the processing time is reduced hundredfold. Recommended technology may be in demand at mining enterprises with the prospect of transition to underground mining.

The main provisions of the Concept of Sustainable Development, formulated in 1992 at the conference in Rio de Janeiro, based on the economy – environment – society sustainability triad, are accepted as the basis for development by most countries. Over the past period, an institutional framework for sustainable development has been formed both at the international level and at the level of states. Reducing level of air pollution is one of the key tasks, solution of which is necessary to achieve the 2030 Sustainable Development Goals stated by the United Nations. Despite of adoption of the Concept of Transition to Sustainable Development in Russia back in 1996, focus on environmental component took a long time to be made. The article considers the stages of regulatory environment development aimed at ensuring sustainable development and reducing level of air pollution in Russia. It was revealed that a significant expansion of the regulatory and legal field in this area occurred only in 2017 – 2019. In many ways, this is due to Russia’s orientation towards achieving the 2030 Sustainable Development Goals stated by the UN, and adoption of the national development goals of the Russian Federation. It was found that despite the use of such financial mechanisms as the state program of the Russian Federation “Environmental Protection” and the national project “Ecology” to achieve sustainability goals, the share of environmental protection expenditures in total expenditures of the federal budget in 2019 was only 1.3 %. At present, in twelve cities of the Russian  Federation, level of air pollution is assessed as high and very high. In seven of them, ferrous metallurgy enterprises operate, which exert significant anthropogenic pressure on the environment.

Experimental studies of the flow of liquid metal in CCM mold are long, complex and labor consuming process. Therefore, mathematical modeling by numerical methods is increasingly used for this purpose. The article considers a new technology for liquid metal supply into a mold. The authors present original patented design of the device, consisting of direct-flow and rotating bottom nozzles. The main results of investigations of the melt flow in the mold are considered. The objects of research were hydrodynamic and heat flows of liquid metal at new process of steel casting into a CCM mold of rectangular section. The result is spatial mathematical model describing flows and temperatures of liquid metal in the mold. To simulate the processes occurring during metal flow in the mold, special software was designed. Theoretical calculations are based on fundamental equations of hydrodynamics, equations of mathematical physics (equation of heat conduction taking into account mass transfer) and proven numerical method. The area under study was divided into elements of finite dimensions; for each element, resulting system of equations was written in difference form. The results are fields of velocities and temperatures of metal flow in the mold volume. A calculation program was compiled based on developed numerical schemes and algorithms. An example of calculation of steel casting into a mold of rectangular cross-section, and flow diagrams of liquid metal along various sections of the mold are given. Vector flows of liquid metal in different sections of the mold are clearly presented at different angles of rotation of the deep-bottom nozzle. The authors have identified the areas of intense turbulence. Metal flows of the described technological process were compared with traditional metal supply through a fixed bottom nozzle.

The research work is devoted to the control of materials structures described on the basis of fractal representations. The formation of fractal structures of materials is carried out due to positive feedback. The article describes the first stage of the work – statements of the problem of identification of materials structures based on fractal representations. Many recent studies indicate the fractal nature of material structures, while the mechanisms of positive feedbacks are based on the generation of fractal structures. At the present stage, the fundamental physicochemical laws governing the emergence and transformation of material structures are developed and presented in such a way that it is difficult to use them for the synthesis of structure control algorithms. In other words, they do not meet the requirements of control models – they do not reflect the dependence of the output actions on external factors. Therefore, it seems useful to go along the path of creating fractal models of structures that are identification structures of materials and then development of control actions, in particular on the parameters of positive feedback for predicting and changing the material structure in the required direction. This corresponds to the method of control algorithms synthesis with an assessment of the control object state and choice of controller gain coefficient. In this work, the statements of the problem of identification images of natural materials structures are formulated. Firstly, fractal models are built using well-known (standard) fractals, and secondly, fractal models are generated using the fractal structure formation mechanism. In the future, these statements of the problem will be used to develop methods and algorithms for materials structuresidentification in various industries, including mining and metallurgical industries.