No 5 (2024)

The article considers a combined technology which mixes selective laser melting (SLM) and longitudinal rolling of powder materials 12Cr18Ni10Ti and AlSi10Mg. The objective of the work is to experimentally establish the regularities of pressure treatment on the mechanical characteristics of the obtained SLM materials, namely on hardness and bending strength. A literature review was prepared, based on the information from which a batch of test samples were made from powders of stainless steel 12Cr18Ni10Ti and aluminum alloy AlSi10Mg. Pressure treatment of the resulting samples was performed using longitudinal rolling technology. The assessment of the high-altitude deformation of the 12Cr18Ni10Ti alloy samples was carried out using true (logarithmic) high-altitude deformation. The morphology of the raw materials was studied using an electron microscope. The mechanical properties of the materials were assessed by HRB hardness and bending strength. The results of radial compression tests on annular samples manufactured under similar technological parameters were analyzed additionally. Based on the results of the analysis, the dependence between stress and deformation was established, where for AlSi10Mg there is a smooth shape change under load, and for 12Cr18Ni10Ti there is a critical stress, at which an increase in deformation dynamics is observed. Scanning electron microscopy of the fractures of the AlSi10Mg material showed a more homogeneous structure of the rolled sample compared to the sample in the initial state, which is evidence of the positive effect of pressure treatment (within certain limits) on the density of the AlSi10Mg material obtained by the SLM method. Based on the results of the researches, a hypothesis about the interdependence of high-altitude deformation and hardness of the cold-deformed material 12Cr18Ni10Ti obtained by SLM was formulated and confirmed by the results of experiments. The bending strength limit of the AlSi10Mg powder material was established and the maximum bending loads for the 12Cr18Ni10Ti alloy was fixed. The dependences between stress and deformation of materials under radial compression and bending are shown. It has been found that longitudinal rolling of 12X18H10T powder material helps to reduce the resistance to bending force, but at the same time the hardness and elastic properties increase.

Now the main industrial method for producing stainless steel is smelting in an argon-oxygen decarburization (AOD) furnace, therefore the paper presents the results of thermodynamic modeling of the desulfurization process of low-carbon semi-finished stainless steel during the reduction period of AOD process by treating it with boron-containing slags. The use of boron oxide as a fluxing material instead of fluorspar reduces the environmental harm and decrease the viscosity of the formed slags. Using the simplex lattice method of experiment planning, a matrix was constructed containing 16 compositions of the oxide system СаО–SiO₂–(3-6%)В₂О₃–12%Cr₂O₃–3%Al₂O₃–8%MgO with variable basicity of 1.0–2.5. Based on the generalization of the thermodynamic modeling results, approximating mathematical models in the form of a reduced third-degree polynomial were constructed. The adequacy of the models is verified by three control points not included in the experimental design matrix using the t-criterion at a significance level of 0.01. The results of mathematical modeling are presented graphically in the form of diagrams of the dependence of the equilibrium sulfur distribution on the slag composition at temperatures of 1600 and 1700°C. The constructed diagrams made it possible to quantitatively estimate the effect of temperature, basicity and boron oxide content on the equilibrium interphase distribution coefficient of sulfur. It is found that an increase in slag basicity from 1.0 to 2.5 in the considered range of boron oxide content (3.0–6.0%) improves the metal desulfurization process, ensuring an increase in the equilibrium interphase distribution coefficient of sulfur from 0.1 to 5.0–7.0 at temperatures of 1700 and 1600°C. It’s shown that the process of metal desulfurization in slags with low basicity of 1.05–1.15 is accompanied by a slight decrease in the sulfur content in the metal. At the same time, the concentration of boron oxide has virtually no negative effect on the process of metal desulfurization. Slags with increased basicity up to 2.0–2.5 have more favorable refining properties. The sulfur concentration in the metal during their formation decreases from 0.015 to 0.007–0.008%.

The results of an experimental study of the normal integral and normal spectral emissivity of technical cadmium and zinc are presented. The choice of the objects of study was due to the lack of literature data on the emissivity of these metals in the open press. The measurements were carried out by the absolute radiation method in an inert gas atmosphere. The results of the change in the intensity of the normal integral emissivity depending on the temperature with the fixation of the surge in the phase transition region are obtained. The normal spectral emissivity of solid polished metals in the melting region was investigated from 0.26 to 10.6 μm. A computational experiment was conducted using the Foote and Drude approximations.

This article discusses the interaction of chemical elements in the three-component Al-V-B system. Vanadium reduces electrical conductivity in primary aluminum, which requires its reduction during aluminum electrolysis to values less than 0.02%. In order to reduce the concentration of vanadium impurities, thermodynamic calculations were carried out for the reactions of separation of the metallic phase of aluminum and impurities of vanadium intermetallic compounds through the use of a boron-containing flux. The calculation of thermodynamic parameters was carried out in HSC Chemistry 9.0. for AlB₂ and VB₂ compounds, the chemical reaction AlB₂ + V = VB₂ + Al within the operating temperatures of electrolysis and casting of primary aluminum of 650–950°С and the conditions of immersion of boron-containing flux into the melt to a ladle depth of 0.5, 1.0, 1.5 and 2 m, i.e. within the pressure range of 102.39–148.99 kPa. Thermodynamic analysis showed that the Gibbs energy (ΔG_T) values in the entire range of operating temperatures of the electrolysis and casting of primary aluminum for VB₂ are significantly lower than AlB₂, therefore, they will be formed predominantly in this temperature range. The order of stability also suggests that vanadium can be easily removed from aluminum melts by adding boron. The results obtained allow us to conclude that chemical reactions of primary aluminum purification from vanadium impurities can occur due to boron additives.

The possibility of using silicon-based anodes in lithium-ion power sources is actively investigated due to the increased lithium capacitance of silicon. This work reports the preparation of submicron silicon fibers on glassy carbon in KI–KF–KCl–K₂SiF₆ melt at 720°C. For this purpose, the parameters of silicon electrodeposition in the form of fibers were determined by cyclic voltammetry, experimental batches of ordered silicon fibers with an average diameter from 0.1 to 0.3 μm were obtained under galvanostatic electrolysis conditions, and using the obtained silicon fibers, anode half-cells of lithium-ion current sources were fabricated and their electrochemical behavior and behavior under multiple lithiation and delithiation were studied. By means of voltammetric studies, it is observed that charging and discharging of the anode based on the obtained silicon fibers occurs at potentials from 0.2 to 0.05 V and from 0.2 to 0.5 V, respectively. Cycling of electrodeposited silicon fibers in anode half-cells of lithium-ion power source was carried out. Depending on the charge current, the discharge capacity ranged from 200 to 500 mAh/g at Coulomb efficiency of 98–100 %. Also, multiple cycling of the sample of lithium-ion power source with a lithium counter electrode was performed. In the course of 800 cycling with current 0.5C, the discharge capacity of the sample decreased from 165 to 65 mAh/g. Scanning electron microscopy shows the volumetric expansion of the of silicon fibers during cycling.