The paper summarizes the results of work done by the group of authors over many years on the direct reduction of heavy non-ferrous metals directly from sulfide compounds contained in concentrates (lead) and metallurgical products (copper, nickel) – white matte, copper and nickel concentrates of converter matte separation. In modern technology the recovery process itself includes the conversion of metal sulfides into oxygen compounds (oxidizing and sintering roasting) with the reduction of metals by carbon-containing reagents (coal, CO), as well as the reduction of copper and, partly, lead from oxide melts by sulfides. Sulfide conversion and reduction operations are associated with the release of sulfur- and carbon-containing compounds (SO₂, SO₃, CO, CO₂) and, consequently, with the need to capture and utilize gaseous and solid products. A fundamentally new process of direct reduction of metals from sulfides using their own sulfide sulfur as a reducing agent is proposed. The recovery process is implemented through the possible formation of short-circuited electrode pairs in the 2Me^z+–zS^2– system due to the implementation of donor-acceptor interactions, primarily π-binding. Successful process implementation is possible with the removal of electrochemical reaction products (product), in particular S⁰. Caustic soda is proposed as such a reagent. Using the example of a number of the above production materials, the possibility of metal reduction at temperatures of 550–700 °C is shown with the achievement of their deep extraction (over 99 %). Elemental sulfur, a product of sulfide sulfur oxidation, reacts with the caustic soda melt and accumulates in the form of non-volatile sodium compounds.

Highly efficient autogenous methods introduced for smelting copper sulfide concentrates led to large volumes of copper-rich slags produced. Existing methods for their processing (such as flotation, various methods of reduction smelting) in separate units are ineffective and require significant costs. The use of Vanyukov furnaces for copper concentrate processing allows for slag reduction treatment in the furnace itself by creating a separate recovery zone. Due to the need for depleting copper-containing slags, the possibility of their reduction treatment was investigated. For these purposes, the feed including copper concentrates and quartz flux was subjected to oxidizing smelting at t = 1280÷ ÷1300 °C several times. The resulting slags were subjected to reduction treatment and analyzed using thermal, X-ray phase, mineralogical, electron probe and chemical analysis. The complete melting temperatures of oxidizing smelting slag samples are noted in the range of t = 1225÷ ÷1280 °С. According to mineralogical studies, the main phases of these slags are magnetite (Fe₃O₄) and fayalite (2FeO·SiO₂) represented by large grains. In addition, the samples contain sulfide compounds: chalcosine and bornite solid solutions (Cu₂S–Cu₅FeS₄), sphalerite (ZnS), galena (PbS). Slag reduction treatment was carried out at t = 1300 °С in the presence of activated carbon following by a decrease in the copper content in slags by an average of 0.45–0.65 % with the magnetite content reduced by 3.6–3.8 times. Slag samples featured strongly pronounced large fayalite crystals where the faylaite content increased sharply due to magnetite reduction with metallized phases reach in lead and zinc concentrated on grain boundaries. Reduction treatment intensifies the following transformations: the transition of iron from one oxidation state to another (Fe³⁺→Fe²⁺) to form fayalite, coalescence of sulfide inclusions, and formation of a matte phase containing copper and iron. During the reduction treatment of slags, lead and zinc can be sublimed with their further extraction.

This study presents the characteristics of the Koni Mansur (Tajikistan) galena concentrate along with the kinetic study results for its leaching in the nitric acid solution. The main minerals (phases) of this concentrate are galena (PbS), sphalerite (ZnS), pyrite (FeS₂), chalcopyrite (CuFeS₂), anglesite (PbSO₄) and quartz (SiO₂). The study uses a sample of the concentrate with the following chemical composition, wt.%: Pb – 46.56, Zn – 4.01, Fe – 20.55, Cu – 2.03, S – 21.78, Si – 3.78 and Al – 1.29. The concentrate particle size varies between 0.84 and 148.26 μm. Optimal conditions for the concentrate nitric acid leaching are found to be: temperature t = 55÷65 °C, acid concentration 1.5–2.0 M and the time of concentrate and acid mixture processing 70–90 min. The leaching of concentrate minerals in the acid solution follows the shrinking core mechanism, at 45–65 °C within the kinetic region and with activation energy E = 46.78 kJ/mol. At temperatures below 45 °C, the concentrate nitric acid leaching reaction is inhibited by acid diffusion transfer to the surface of particles with activation energy E = 12.4 kJ/mol. The concentrate processing flow chart is proposed based on the kinetic study results obtained for the mineral leaching process with its main stages described as zero-emission and zero-waste, environmentally friendly, and implemented in a closed cyclic mode with nitric acid regeneration. This results in a significantly cost-effective route for the concentrate leaching process. The resulting associated chemicals are valuable for use in a wide range of industries.

It was found that when the tungsten anode is electrochemically dissolved in a melt of acidic alkali metal fluorides (K,Na)H₂F₃ and hydrogen fluoride at t ~ 37 °C, the resulting atomic fluorine reacts completely with tungsten to form tungsten hexafluoride (WF₆). The latter dissolves in the melt to form complex compounds (K,Na)₂WF₈ and (K,Na)WF₇, which is accompanied by an increase in the melting electrolyte point. Adding up to 23 mol.% LiF and WF₆ electrolyte saturation lower the electrolyte melting point below 18 °C making it possible to obtain simultaneously gaseous WF₆ at the anode and H₂ at the cathode in an electrochemical process at t = 35÷40 °C and an anode current density of 0.3–0.5 A/cm². During gas-phase deposition of tungsten, dense layers are formed from the resulting gas-containing mixture with a stoichiometric ratio of components at t = 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. A short fluoride cycle in the tungsten technology is presented based on the results obtained. It uses two operations: electrochemical synthesis of the WF₆+H₂ gaseous mixture in an electrolyzer with a bulk anode made of metal tungsten fragments, and WF₆ reduction by hydrogen with capture the resulting HF. This cycle reduces the chain of process units in the cycle by almost 2 times with a corresponding investment reduction and significant production cost saving. The paper provides process flow diagram of the production chain for environmentally friendly tungsten production with a capacity of ~48.5 tons per year, which can be replicated and modified to produce the necessary products.

Scanning electron microscopy (EDS analysis), magnetic force microscopy (MFM) and nanoindentation were used in the metallographic study of the magnetic structure and nanomechanical properties of sintered USC-20L Nd–Dy–Fe–B rare-earth magnets (Ural Strip Casting Technology). The microstructure of the sintered USC-20L Nd–Dy–Fe–B magnet includes the Nd₂Fe₁₄B phase grains separated by lamellas of neodymium-rich phases. Nd–29.1%Fe–6.2%C–2.2%O–1.4%Dy inclusions are located at the triple junctions of Nd₂Fe₁₄B grains. Nd–4.5%Fe–9.1%O–6.7%C–4.5%Fe–2%Dy inclusions are located along grain boundaries and contain neodymium and dysprosium oxides. The chemical composition of grains: Fe–25%Nd–6.9%C–1.6%Dy–1.4%B. It was found that due to irregular grain growth, the neodymium-rich phase interlayers are connected to each other in the region of grain junctions causing internal stress concentration and cracking. A crack propagates along the grain boundary from one wetted grain joint to another due to the occurring mechanical stresses. A phenomenon of intergranular wetting by the neodymium-rich phase is observed at Nd₂Fe₁₄B/Nd₂Fe₁₄B grain boundaries. It was found that Nd-riched phases can pseudo-incompletely (or pseudo-partially) wet such grain boundaries, i.e. form a non-zero contact angle along the grain boundaries and in triple joints. Based on the magnetic force microscopy results, a conclusion was 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 size of the banded-structure domain is ~1 μm, domain wall energy is γ ~ 14 kJ/m², domain wall width is δ ~0.6·10^–9 m. The nanoindentation method was used to measure the values of nanohardness (H, GPa), elastic modulus (E, GPa), contact stiffness (S, N/m), elastic strain energy (W_e, nJ) and plastic strain energy (W_p, nJ) in submicrovolumes of Nd₂Fe₁₄B grains. According to the measurement results, the minimum value of Nd₂Fe₁₄B grain adhesion was estimated: K_int = 0.539 MPa·m^0.5.

The paper presents the results of research on the synthesis of Al–Si–Mg (AK7ch), Al–Si–Mn (AK12), Al–Si–Cu–Mg (AK6M2) and Al–Mg–Mn (AMg5) aluminum alloys using dispersed waste: beverage cans (Al–Mn–Mg system), cast alloy sawdust (Al–Si–Mg system), twisted chips of Al–Cu–Mg and Al–Mg–Mn deformable alloys. The waste microstructure was studied in the initial state, and the typical sizes of main phases were determined. The main criteria for the quality of recyclable waste were determined: purity (k_p), contact with the atmosphere (k_a) and maximum metal recovery (М_Ме). Based on the proposed criteria, the waste was graded according to recycling efficiency. Can waste received the lowest total score, and AK9ch alloy sawdust had the highest score. Experiments on the synthesis of Al–Si–Mg (AK7ch), Al–Si–Mn (AK12), Al–Si–Cu–Mg (AK6M2) and Al–Mg–Mn (AMg5) alloys demonstrated that the yield varies from 82 to 96 %. The minimum yield was observed for the AK12 alloy with can waste predominating in the charge composition. The chemical compositions of alloys in terms of the content of the main alloying and impurity elements met the regulatory documentation requirements. Mechanical tests showed that synthesized alloys have a guaranteed margin of strength and plasticity in comparison with regulatory documentation requirements. Metallographic studies revealed that the microstructure of synthesized alloys is free from non-metallic inclusions and gas porosity. Non-modified and modified Al–Mg–Mn (AMg5) alloy samples were subjected to cold rolling in several passes until cracking. The non-modified alloy sample began to crack after the 10th pass. The modified alloy sample withstood 12 passes before cracking. The degree of deformation over the sample thickness was 60.5 % for the non-modified alloy, and 67.2 % for the modified alloy.

The study covers the manufacturability and properties of sheet metal obtained from a large-sized ingot of Alloy 1580 with the low scandium content within its grade range. The ingot processability in hot and cold rolling was evaluated, and the influence of the degree of deformation and annealing conditions on the properties of cold-rolled semi-finished products made of the alloy under study was investigated. A large-sized commercially produced ingot with a cross section of 500×2100 mm of Alloy 1580 with a scandium content of 0.067 wt.% was selected as an object of research. The research methodology included several stages of rolling and heat treatment of semi-finished sheet products at various stages of the developed mode for metal deformation and mechanical testing of samples from them on the LFM 400 kN universal machine. For research, a 60×500×900 mm template was cut from the ingot to make 50×180×300 mm billets for rolling. Billets were subjected to homogenization annealing by the two-stage mode developed previously for this alloy. As a result of hot rolling of annealed billets at 450 °C and a total relative compression ε_Σ = 84÷90 %, 5–8 mm thick semi-finished sheet products were obtained. Further, after their annealing at t = 320 °C for 6 hours, light-gauge semi-finished sheet products with a thickness of 2 to 6 mm were manufactured by cold rolling. They were subjected to mechanical analysis in the deformed and annealed states. The analysis of their mechanical properties in the deformed and annealed states was performed, which showed that the accumulation of the total degree of deformation during cold rolling up to 38 % provides the 1580 alloy with an increase in strength properties to R_p = 380 MPa, and after that the growth rate slows down and at ε_Σ = 60 % R_p = = 400 MPa. The effect of annealing at temperatures between 250 °C and 350 °C on the mechanical properties of sheet metal. It was found that it leads to a decrease in strength properties and an increase in ductility, and the maximum yield strengths correspond to annealing temperatures of 250–275 °C at a sufficiently high plasticity. As a result of studies, it was found that the strength properties of sheet metal from Alloy 1580 with a low scandium content exceed the strength properties of semi-finished products of Alloy AW-5083 (USA) having a similar chemical composition, but without the addition of scandium, by 10–15 %, and the excess in plastic properties is 40–60 %.

The effect of deformation modes on the process conditions of radial-shear rolling (RSR) of commercial purity aluminum AA1050 is analyzed. Based on finite-element modeling (FEM), temperature variation at various feed angles and elongation in the first and last passes is obtained. An increase in the feed angle slightly raises temperature fluctuations in the surface layer due to increasing reduction per pass, but it does not significantly influence the total deformation heating during RSR. The final deformation temperature can be controlled by varying the reduction ratio. In this case, it is necessary to take into account the initial heating temperature, dimensions of final rolled products and elongation per pass. The billet size has a significant effect on thermal variations during RSR. In the last pass, when diameters are 20–14 mm, deformation heating is almost completely compensated by rod cooling in contact with the environment and the tool and begins to prevail with an increase in the elongation ratio of more than 1.2. The analysis of equivalent strain (ε_e) at various deformation modes showed that the difference in ε_e values over the rod cross-section decreases with the increasing feed angle. A comparison of the data obtained with the hardness and microstructure of rolled AA1050 samples shows that ε_e has a significant effect on changes in the structure and properties to a certain value. This is confirmed by the obtained microhardness distribution over the cross section of rods. Mechanical properties of obtained rods correspond to the properties of commercial purity aluminum in the work hardened condition (σ_в ~ 115 MPa, σ_0.2 ~ 110 MPa, δ ~ 1 %, HV ~ 40÷43).