In the current context of declining reserves of high-grade copper sulfide ores, oxidized ores are becoming an important source of mineral raw materials containing non-ferrous and precious metals. Traditional flotation processing of these ores results in low-grade concentrates with poor metal extraction rates (40–60 %). Heap leaching is considered the most promising method for processing such ores. As a result of prolonged intensive mining at the Erdenetiin Ovoo deposit (Erdenet, Mongolia), approximately 800 million tonnes of oxidized ore dumps with an average copper content of 0.45–0.48 % have accumulated within the open-pit boundary. Global experience in processing such secondary raw materials demonstrates the high economic efficiency of copper extraction through heap leaching, followed by solvent extraction and electrowinning (SX-EW) of copper from the pregnant leach solution. For the State-owned Enterprise Erdenet, it is essential to conduct leaching studies on oxidized ores and pilot testing of this technology on the ore from existing ore dumps. To achieve this, 35 boreholes were drilled in the dumps (16 in dump No. 8a and 19 in dump No. 12), from which core samples were collected. The mineralogical composition of the oxidized copper ore samples was analyzed, and the effect of heap leaching parameters (ore particle size, solution acidity, etc.) on copper recovery into the pregnant leach solution was determined. To more accurately assess the recoverable copper from the two dumps, composite samples were collected from each borehole, and large-scale heap leaching tests were conducted in 30 open-cycle columns. The test results showed that copper extraction rate from dump No. 8a ranged from 35.8 % to 69.1 %, with an average of 56.0 %, while dump No. 12 exhibited extraction rates ranging from 51.8 % to 77.4 %, with an average of 63.6 %.

The study presents the results of gold dissolution in cyanide solutions using the cyclic voltammetry method. A methodology was developed to investigate the mechanism of gold leaching in cyanide solutions by determining the relationship between current and potential under varying cyanide and oxygen concentrations. It is known that as the electrode potential increases, the gold dissolution current rises until the passivation potential is reached, after which it sharply decreases due to the formation of an oxide film, resulting in gold passivation. It was established that the maximum passivation current is achieved at oxygen and sodium cyanide concentrations of 7.5 mg/dm³ and 300– 400 mg/dm³, respectively. Mathematical relationships for the passivation potential and current as functions of sodium cyanide and oxygen concentrations were determined, described by polynomial equations with approximation coefficients R₂ > 0.7. When the polarization direction is reversed, the current polarity changes, producing a cathodic curve with a peak at the depassivation potential, corresponding to the dissolution of the passive gold film. The depassivation potential and current show weak dependence on sodium cyanide concentration. The cyclic voltammetric curve terminates at the initial point with the same current and potential values, indicating the complete removal of the oxide film from the gold surface. The oxide film thickness, calculated based on the amount of passed charge, was found to be 0.007 μm. Metallographic studies demonstrated that the film thickness could not be determined by this method. A gold surface diffractogram revealed that the passive film formed after heating to 125 °C has the crystallochemical formula Na_0.66Au_2.66O₄. The study highlights the potential for enhancing gold recovery from refractory ores through electrochemical treatment in alkaline conditions.

Cast master alloys of the Mo–Cr, W–Cr, and Cr–Al systems with high chromium content were produced using the methods of centrifugal SHS metallurgy. A thermodynamic analysis was performed to evaluate the combustion temperature and the equilibrium composition of the reaction products depending on the ratios of the initial components in the mixture. Based on this analysis, optimal compositions were identified for further experimental studies. The effectiveness of functional additives, namely calcium fluoride CaF₂ (fluorspar) and sodium hexafluoroaluminate Na₃[AlF₆] (cryolite), was experimentally confirmed. These additives were shown to lower the melting point of the slag phase (reducing its viscosity), which facilitated phase separation during the production of cast master alloys from refractory metals using centrifugal SHS metallurgy. The experiments demonstrated the need to introduce excess amounts of MoO₃ and WO₃ during the production of Mo–Cr and W–Cr master alloys, respectively, due to incomplete reduction of molybdenum and tungsten from their oxides. Microstructural analysis of the obtained master alloys revealed a dendritic structure, which is typical for cast materials. EDS microanalysis showed that the chemical compositions of all synthesized alloys closely matched their calculated and target compositions. Composition analysis at different locations within the ingots revealed no significant variations in composition. X-ray phase analysis confirmed the presence of solid solution phases formed from the target elements. The results of inductively coupled plasma mass spectrometry (ICP-MS) confirmed that the chemical compositions of the synthesized Cr–W, Cr–Mo, and Cr–Al alloys fully comply with the permissible concentrations of both target elements and impurities.

In the investment casting process, in addition to wax patterns, water-soluble salt patterns made of urea are also used. It is known that urea-based patterns provide high strength and allow the patterns to maintain their shape even if the temperature in the foundry increases. However, due to environmental and production-related reasons, there is currently a growing demand for transitioning to a technological process involving colloidal silica binder. This transition presents challenges related to the manufacturing of ceramic shell molds due to the interaction between the pattern compound and the colloidal silica binder slurry. This study examines the effectiveness of protective coatings based on repair wax, varnish (AK 593), and varnish with rosin, applied to water-soluble urea-based patterns containing additives such as magnesium sulfate, potassium nitrate, polyvinyl alcohol, and dimethylglyoxime. The degree of interaction was assessed by measuring the wetting angle and the spreading area of the colloidal silica binder over the surface of pattern samples with various coatings. It was found that all coatings contributed to an increase in the wetting angle and a reduction in the spreading area. Additionally, ceramic molds and castings made of nickel superalloy were produced using a series of pattern compounds with protective coatings. The surface roughness and dimensional accuracy of the castings were evaluated. It was demonstrated that the protective properties of the repair wax-based coating were insufficient, leading to the formation of cracks and sagging in the mold. This resulted in penetration defects in the castings and a significant decrease in dimensional accuracy. In contrast, when using coatings based on varnish and varnish with rosin, no defects were observed in the mold or castings, making these coatings recommended as protective solutions for urea-based pattern compounds in contact with colloidal silica binder slurries.

Recently developed aluminum alloys based on the eutectic composition of the Al–Ca system exhibit excellent casting properties and, unlike silumins, show good deformability. The development of multi-component alloys, where calcium is partially replaced by lanthanum, cerium, nickel, and other eutectic-forming elements, improves their properties by producing a finer eutectic structure and enhancing their heat resistance. These alloys can all be strengthened through deformation, with severe plastic deformations being especially effective. Among these methods, rotary forging is of particular interest due to its ability to produce long billets. Lanthanum, at a specific concentration, significantly improves the alloy’s plasticity, making the Al–La system particularly well-suited for deformation processing. This study investigates the effect of rotary forging on the microstructure and mechanical properties of two eutectic alloys, Al–10La and Al–6Ca–3La (wt. %). Billets in the as-cast state were rotary forged from an initial diameter of 20 mm to a final nominal diameter of 5 mm under isothermal conditions: at room temperature for the Al–10La alloy and at 200 °C for the Al–6Ca–3La alloy. The results showed that rotary forging led to an elongated structure in both alloys, with micron-sized grains forming inside the dendrites and eutectic particles being refined. In the Al–10La alloy, the dislocation density was low, while in the Al–6Ca–3La alloy, the dislocation density was higher. The Al–10La alloy showed a slight tendency to soften during rotary forging, whereas the Al–6Ca–3La alloy exhibited a marked tendency to strengthen (its strength doubled). Both alloys retained high plasticity (elongation) after forging. After annealing at 300 °C, the strength of both alloys remained stable. The tensile strength of the Al–6Ca–3La alloy at 300 °C was higher than that of the Al–10La alloy, with values of 53 MPa and 44 MPa, respectively.

The effect of thermo-mechanical treatment on the structure and mechanical properties of the hot-rolled orthorhombic titanium aluminide alloy VIT1 was investigated. The evolution of the microstructure and mechanical behavior of the alloy during hot deformation in the temperature range of 850–1050 °C was studied. It was established that at a temperature of 950 °C, a strain rate of ε· = 5 ·10^–4 s^–1 and a strain of ε = 70 %, the microstructure formed during hot deformation, due to the processes of recrystallization and spheroidization, consisted of grains ~1 μm in size, comprising β-, α₂-, and O-phases. It was shown that increasing the deformation temperature led to the dissolution of O-phase particles and a significant deceleration in the development of dynamic recrystallization. Homogeneous fine-grained billets were obtained via multi-directional isothermal forging, and the effect of heat treatment (quenching and aging) on the structure and mechanical properties of the alloy was examined. Based on a preliminary study of the influence of heating temperature on the alloy’s structure and properties, the temperature ranges for quenching and aging were determined. It was demonstrated that the most balanced levels of strength, ductility, and heat resistance were achieved after heat treatment under the following conditions: holding for 4 h at 1025 °C followed by air cooling, and aging at 850 °C for 6 h.

This study investigates the process of enhancing the efficiency of the afterburning chamber in the Vanyukov furnace. Various operational modes of the furnace and the chamber were analyzed to identify optimal conditions for sulfur oxidation and afterburning, as well as methods for reducing accretions. Measurements and analyses of off-gas compositions were conducted, and the dust content was determined.
Simplifications and assumptions were applied in the calculations, enabling the modeling of gas flow, thermodynamic processes, velocity profiles, and interaction zones. Some thermodynamic calculations of counter-penetrating gas jets were based on hypotheses derived from heat exchange theories in mixing devices. Experimental results of numerical modeling and predictive simulations within the afterburning chamber are presented. Parameters were measured, and aerodynamic characteristics of the tuyeres were charted at an average oxygen supply to the chamber of no more than 2500 n.m³/h (38 n.m³ per ton of batch load). Recommendations for effective technological operations were proposed. The expertise of specialists from the Sredneuralsk Copper Smelter, along with the results of trials and process modeling, facilitated the selection of the optimal tuyere air distribution. The findings reveal the complexity of aerodynamic and thermodynamic processes occurring within the afterburning chamber. These include interactions between tuyere cooling airflows, heat release from exothermic oxidation reactions, and forced and natural convection of off-gases with varying temperature gradients, all visualized within a single projection.