Vol 57, No 1 (2016)

The topicality is shown to improve the processing technology of complex polymetallic raw material containing a considerable amount of toxic impurities of arsenic and lead. Results on pressure leaching the mattes formed after reduction smelting the dusts of OAO Sredneural’skii Copper Smeltery (SUMZ) by solutions of copper sulfate are discussed. These mattes contain a considerable amount of lead and arsenic. According to the data of X-ray phase analysis of matte samples, phases of sulfides (PbS, PbS ⋅ As₂S₃, Cu₂S, FeS, and (Zn,Fe)S) and arsenides (FeAs₂, Cu₃As, FeAs, and Cu_0.85As_0.15), as well as inclusions of metallic copper, are revealed in them. Optimal parameters of matte leaching by copper sulfate solutions are the temperature of 150–180°C, acidity from 5 to 30 g/dm³, and copper concentration of 14–32 g/dm³. This process made it possible to extract 85% As into the solution, while copper and lead remained in the cake in this case.

The continuous extrusion (the Conform method) of a noncompact aluminum material of the Al-Mg system is investigated. The experimental data on the variation in temperature and energy-power process parameters are found. An analysis of the variation in temperature and hydrostatic pressure in the zone of the deformation treatment is implemented. Seven zones which qualitatively characterize the extrusion of a noncompact material are revealed during this analysis. An essential nonuniformity of the hydrostatic pressure in the deformation region, which governs the inhomogeneity of the properties of prepared billets, is observed.

Bulk metallic glasses (BMGs) of Pd–Cu–Si and Pd–Ni–P systems were formed from a melt in the 1970s–1980s. However, in view of the extremely high cost of the main component (palladium), they have been outside the realm of special interest of scientists and engineers for a long time. Relatively recently, BMGs in the form of macroscopic-sized ingots have been fabricated in alloys based on industrial metals (iron, copper, magnesium, and titanium), which opened up wide possibilities for their application. BMGs possess high strength, hardness, wear resistance, elastic deformation, and corrosion resistance. In this study, a review of publications is presented and main scientific achievements in this field are described. It is noted that main scientific problems, which are not solved completely, are describing the BMG structure as well as vitrification and plastic deformation, while the technical problem attracting the attention of scientists in many countries is to increase the plasticity and impact fracture toughness of these materials.

A one-stage manufacturing technology of aluminum–ceramic skeleton composites by combining the processes of self-propagating high-temperature synthesis (SHS) of a porous skeleton formed by the MAX phase of the Ti₂AlC composition and its impregnation by the aluminum melt under pressure (SHS compaction) is considered. A composition of the exothermic charge 2Ti + C + 22.5 wt % Al + 10 wt % TiH₂, which provides the formation of a porous skeleton of the Ti₂AlC phase without impurity phases by the SHS technology, is selected. It is shown that, when impregnating the hot SHS skeleton with aluminum, new phases are formed such as the MAX phase (Ti₃AlC₂), titanium carbide (TiC), and titanium aluminide (Al₃Ti). However, the content of the basic MAX phase remains high, and the ceramic component of the material consists of Ti₂AlC by 76%. When analyzing the microstructure, it is revealed that the composite has certain residual porosity after impregnation and cooling. The influence of the impregnation pressure (q = 22, 28, and 35 MPa) on the distribution of the aluminum content over the height and radius of the diametral sample section is investigated experimentally. It is shown that the nonuniform Al distribution over the sample bulk is caused by the nonuniform pressure and temperature fields, as well as the different compactibility of hot inner and colder outer sample parts. The degree of compaction of characteristic zones is leveled as the impregnation pressure increases, and the composition inhomogeneity over the sample bulk decreases. The difference in aluminum concentration over the sample bulk at q = 35 MPa does not exceed 5%. The SHS-compacted aluminum–ceramic skeleton composite based on the Ti₂AlC MAX phase corresponds to high-strength Al-Zn–Mg–Cu aluminum alloys by the hardness level (HB ≈ 150 kg/mm²).

The area of dendritic deposits of zinc deposits prepared by electrolysis from zincate electrolyte, which contained 0.3 mol/dm³ ZnO and 4 mol/dm³ NaOH, is determined. The application of electrochemical methods has made it possible to measure the in situ surface without removing the dendrite deposit from the cathode. The specific deposit surface found using chronopotentiometry is 0.144 ± 0.002 m²/g, while according to the result of impedance spectroscopy it is 11.61 ± 0.14 m²/g. The surface of powders prepared from dendrite deposits is 21.26 ± 0.62 m² according to the data of the BET method. It is shown that the difference in these values is associated with the resolving ability of methods applied. It is established that the surface of dendritic deposits possesses fractal properties. The fractal dimension of the specific surface is calculated and the results of measurements performed by different methods are compared using the scaling relationship.

Shrinkage curves of alloys formed from the WC–8% Ni hard-alloy mixture activated by introducing 10% nanodimensional WC and charge without the additive in a temperature range of 800–1500°C are presented. The pore structure and microstructure of the samples at various stages of sintering are investigated. The peculiarity of densification of the modified alloy, which consists in the shift of the shrinkage curve into the lower temperature region, is revealed. This makes it possible to lower the temperature of the vacuumcompression sintering of alloy, form a finer grain structure, and attain high characteristics of hardness–wear resistance without worsening the strength characteristics. Physicomechanical properties and microstructure of compression-sintered samples made of VN8M activated alloy and standard VN8 alloy without additives are investigated.

Specific features and regularities of reactions of titanium carbide alloyed over the sublattice of nonmetals (N, O) with the nickel melt are analyzed. It is established that the partial substitution of carbon in TiC by nitrogen decreases its dissolution rate in nickel and increases the degree of process incongruence (the transfer of carbon into the melt is preferential compared with titanium). The concentration dependence of the dissolution rate of TiC_xN_z in nickel changes its sign to the opposite one compared with approaching the system to equilibrium. Titanium carbonitride is not recrystallized through the nickel solution as the only phase, and mainly its carbide component is subjected to recrystallization. It is revealed that the partial substitution of carbon in TiC to oxygen increases its dissolution rate in nickel. The dissolution of oxycarbide TiC_0.6O_0.4 in nickel is accompanied by the gradual loss of its carbon until titanium monoxide is formed and by its further disproportionation. The peculiarity of the interaction mechanism of titanium oxycarbides with the nickel melt is determined by reaction [C] + [O] = CO↑ in the liquid phase.

The surface profile, structural features, and phase composition of coatings of the TiB₂–Al system, which were fabricated by electroexplosion sputtering, are investigated by optical interferometry, scanning electron microscopy, and X-ray phase analysis. It is established that posttreatment surface roughness parameter R_a = 2.0 μm. The phase composition of formed layers includes Al, TiB₂, and TiBC₃. Coatings have a cohesion–adhesion bond with the surface-contact material.