The study covers the viscosity of NaF–AlF3–CaF2–Al2O3 conventional cryolite-alumina melts with a cryolite ratio CR = 2.3 depending on the CaF2, Al2O3 content and temperature. The viscosity of cryolite-alumina electrolyte samples prepared under laboratory conditions and electrolyte samples of industrial electrolytic cells was measured by the rotary method using the FRS 1600 rheometer («Anton Paar», Austria). The laminar flow region of the melt determined according to the dependence of viscosity on shear rate at a constant temperature was 10–15 s–1 for all the studied samples. The temperature dependence of cryolite-alumina melt viscosity was measured at a shear rate of 12 ± 1 s–1 in the temperature range from liquidus to 1020 °C. It was shown that the change in the viscosity of all samples in the investigated temperature range (50–80 °С) can be described by a linear equation. The average temperature coefficient of linear equations describing the viscosity of cryolite-alumina electrolytes prepared in laboratory conditions was 0.005 mPа· s/°С, which is 2 times less compared to industrial cell electrolytes. Thus, the change in the viscosity of industrial cell electrolytes with increasing temperature is more significant. Both alumina and calcium fluoride additives increase the cryolite melt viscosity. The viscosity of samples prepared with the conventional composition NaF–AlF3–5%CaF2–4%Al2O3 (CR = 2.3) is equal to 3.11 ± 0.04 mPа· s at an electrolysis operating temperature of 960 °C, while the viscosity of industrial cell electrolytes with the same cryolite ratio is 10–15 % higher and falls in the range of 3.0–3.7 mPа· s depending on the electrolyte composition.

The aim of the research is to develop an optimal method for Sn–Pb alloy processing to obtain a marketable product – high-grade tin O1–O3 (Sn  98.5 %). Laboratory studies were conducted on the refining of the Sn–Pb alloy with the following composition, wt.%: 53–60 Sn; 18–29 Pb, first by vacuum distillation (t = 1085÷1300 °C, P = 15÷100 Рa; τ = 3÷36 h) for As, Sb and Pb sublimation, then by reagent deposition with elemental sulfur and aluminum as part of the Al–Sn master alloy in the presence of NH4Cl for Cu, Fe and Sb separation. This resulted in obtaining a Sn-containing residue (yield ~60 %) of the following composition, wt.%: 92.39 Sn; 0.46 Pb that was subjected to reagent refining to obtain O3 grade tin (metal yield ~68 %) with the following composition, wt.%: 99.5 Sn; 0.009 Pb. It was found that it is feasible to carry out refining from a preliminarily decopperized Sn–Pb alloy to obtain a finished O1 grade product with a direct extraction of 90 %. A schematic diagram was developed and recommendations were formulated for the process regulations on Sn–Pb alloy processing to obtain commercial tin and recover resulting intermediate products and waste. A furnace with separate production of As, Sb, Pb condensates with the following composition, wt.%: 94.2–98.3 As; 5.1–14.5 Sb; 78.9–86.4 Pb, respectively, was chosen as a vacuum distillation unit. The economic effect of processing ~480 ton/year of Sn–Pb alloy (~50.8 % Sn) with the production of ~235 ton/year of O1–O3 grade tin is ~39 million rubles/year.

The paper provides the results of a study on the influence of welding types (laser, electron beam, and TIG welding) on the properties of a permanent connection made of an EP693 alloy of the Ni–Cr–W–Co–Mo system used in the production of gas turbine engine components and parts. EP367 filler wire of the Ni–Mo–Cr–Mn system was used to obtain a weld during laser and TIG welding. A comparative analysis of heating areas and power densities was performed for the welding types studied. It was established that TIG welding features by greater values of the heating area and power density in comparison with laser and electron beam welding. It was found that the type of welding affects the features of weld formation. For example, a weld is formed with the transition to knife fusion penetration in the weld root for electron beam welding, and in the form of an «hourglass» for laser welding. The analysis of the heat affected zone microstructure showed that the smallest grain size is formed during laser welding. The distribution of elements in the weld joint was analyzed. It was found that when welding with the use of filler wire, the Mo content increases and the W, Co, Al, and Ti content decreases in the weld and heat affected zone relative to the base metal. This determines the peculiarities of failure for samples obtained using the welding types studied. Samples obtained by TIG and laser welding broke along the heat affected zone on the weld reinforcement side. Samples obtained by electron beam welding broke along the weld. Mechanical tests of samples at room and elevated temperatures showed that samples obtained by laser and electron beam welding have the highest tensile strength.

The paper investigates the effect of heat treatment modes on the corrosion resistance and strength properties of the EP718 precipitation-hardened nickel-based alloy originally developed for the aircraft industry and currently used in the oil and gas industry. The effect of the annealing temperature (980–1130 °C), holding time (1–2 h) and the time of intermediate and final aging (4–20 h) at 780 °C and 650 °C was studied. It was found that EP718 alloy strength and corrosion properties are determined by the hardening temperature. Highest strength properties are achieved at a hardening temperature of 980 °C (yield strength σy = 950 MPa) due to a higher grain score equal to 3.5 and the presence of inclusions of different size. However, in this case corrosion rate reaches V = 5.88 g/(m2·h). The temperature of 1130 °C ensures the best corrosion performance (V = 2.04 g/(m2·h)) due to the dissolution of undesirable phases (volume fraction of non-metallic inclusions is 0.47 %), but strength performance is reduced (σy = 756 MPa) in this case as a result of the lower grain score – 2.7. Aging mode consisting of an intermediate aging stage with holding at t = 780 °C for 5 h and a final stage at 650 °C for 16 h with air cooling ensures maximum hardening, which is expressed in an increase in hardness to 37.5–38.5 HRC. Electrochemical studies demonstrated that an increase in the aging time leads to a decrease in the stability of the passive state.

A comparative analysis of the phase composition and morphology of primary crystals in hypereutectic alloys of the Al–Ca–Ni–X system (where X is Fe, Si, Mn) was carried out by calculation and experimental methods, including the construction of liquidus surfaces. Additional alloying of the base Al–6%Ca–3%Ni alloy with iron and silicon leads to the formation of coarse elongated primary crystals up to 100 μm in length. It was found that the addition of manganese, on the contrary, leads to the formation of relatively small (average size about 20 μm) compact primary crystals of two four-component phases. Presumably, they are phases based on ternary compounds Al9CaNi and Al10CaMn2. The composition of eutectics in quaternary alloys has been determined. All aluminum-calcium eutectics are characterized by a higher proportion of the second phases, a thinner structure compared to the aluminum-silicon eutectic in AK18 silumin, and are also capable of spheroidization upon heating, starting from 500 °C. The combination of compact and spherical particle morphology after annealing  in the 63-2Mn alloy appears to be favorable for deformation. Comparison of the manufacturability of the experimental alloy Al–8%Ca–1%Ni–2%Mn and the grade silumin AK18 showed the advantage of the former. In terms of the totality of its characteristics, the experimental alloy can be considered as the basis for the development of hypereutectic alloys of a new generation as an alternative to piston silumins of the AK18 type. The experimental alloy, the microstructure of which is characterized by a compact morphology and small size of primary crystals and a fine structure of the eutectic, in contrast to hypereutectic silumins, does not require special modification.

Cermets are ceramic-metal composite materials (composites) with a relatively high content of ceramic phases from 15 to 85 % by volume. In the 20th century cermets were considered mainly as composites of high-temperature carbide, oxide, nitride, boride and silicide ceramic phases with metallic phases of the iron group, but in the 21st century the concept of cermets has significantly expanded due to the appearance of composites made of ceramic and metal phases with lower melting points including sulfides and MAX phases, as well as light and low-melting metals (Al, Mg, Cu, Ag, Pb, Sn). Therefore, cermets began to be considered not only as tool, heat-resistant and wear-resistant heavy structural materials, but also as light, strong structural materials for the production of vehicles, and as functional materials for various purposes. However, quite often cermets are characterized by such disadvantages as a tendency to brittle destruction, the difficulty in achieving structural uniformity and reproducibility, as well as fault detection, and the high cost of cermet manufacturing. It determines the need in their further development, research to improve the composition, structure and properties of cermets, searching for new applications, developing new manufacturing methods and reducing the cost of their production. Various cermet manufacturing methods are discussed such as solid-phase, liquid-phase, gas-phase, and in-situ methods. The methods of infiltration with molten metals, the effect of wetting, and the conditions for spontaneous infiltration are considered in more detail. The results of using the method of self-propagating high-temperature synthesis (SHS) are also described in detail including a new cermet manufacturing method proposed by the authors of this review based on the use of the SHS of a porous ceramic skeleton followed by spontaneous infiltration with molten metal.