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Nº 5 (2024)

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Articles

Properties of cold-deformed powder materials 12Cr18Ni10Ti AND AlSi10Mg obtained by selective laser melting

Boshkanets D., Sergeenko S.

Resumo

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.

Rasplavy. 2024;(5):473-483
pages 473-483 views

Formation of local structural order in the aluminum melt before crystallization

Vorontsov V., Pershin V.

Resumo

The results of an experimental study of acoustic emission spectra (AE) in the frequency range of 20–200 kHz, which occur when the temperature of the aluminum melt decreases from 860 to 660°C. The paper discusses the relationship between acoustic signals and the processes of structural transformations in the melt as the temperature.

Rasplavy. 2024;(5):484-490
pages 484-490 views

The estimation of desulphurization property of boron-containing slags of the reduction period of the AOD process

Babenko А., Upolovnikova А., Kel’ I., Shartdinov R.

Resumo

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%.

Rasplavy. 2024;(5):491-500
pages 491-500 views

Effect of boron oxide and basicity on viscosity and crystallization onset temperature of СаО–SiO2–B2O3–12%Cr2O3–3%Аl2O3–8%МgO slag system

Babenko А., Shartdinov R., Upolovnikova А., Smetannikov А.

Resumo

The rapid growth of demand for stainless steel and, accordingly, its production, which occurred in the second half of the 20th century and continues till today, makes it necessary to conduct studies of the properties of oxide systems that will contribute to the improvement of metallurgical production technologies for such steel. Therefore, in this paper, using the method of simplex grids for experimental planning and vibration viscometry, a study was conducted of the effect of basicity and boron oxide content on the viscosity and crystallization onset temperature of slags of the СаО–SiO2–B2O3–12%Cr2O3–3%Аl2O3–8%МgO oxide system formed during the reduction period of the production of low-carbon stainless steel by the argon-oxygen decarbonization (AOD) process, which is currently the main method for producing corrosion-resistant steel. The introduction of boron oxide into AOD-slags is a possible solution to the problem of instability of the physical properties of slags during smelting, caused by the volatility of fluorspar fluorides, traditionally used as a flux, and compliance with increasingly stringent environmental requirements by eliminating the formation of toxic fluorine compounds. Based on the results of experimental studies of the viscosity of slags of the studied oxide system depending on the chemical composition and temperature, approximating mathematical models in the form of a reduced third-degree polynomial are constructed. Graphically, the results of mathematical modeling are presented in the form of “composition – property” diagrams, which allow quantitatively determining the effect of temperature and chemical composition of the slags under study on viscosity and their composition on the crystallization onset temperature. It is noted that at 1600 and 1650°C, an increase in the boron oxide content in the slag from 3.0 to 6.0% has a favorable effect on the fluidity of the formed slags in the basicity range of 1.0-2.5. For example, an increase in the boron oxide concentration from 3.0 to 6.0% ensures a decrease in the viscosity of the slags from 2.0 to 0.5 Pa s at a temperature of 1600°C and from 0.4 to 0.3 Pa s at a temperature of 1650°C in the region of increased basicity up to 2.0-2.5.

Rasplavy. 2024;(5):501-509
pages 501-509 views

Emissiveness of technical cadmium and zinc

Kosenkov D., Sagadeev V.

Resumo

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.

Rasplavy. 2024;(5):510-518
pages 510-518 views

Physicochemical properties of Na2SO4-CaSO4 melts

Tanutrov I., Sviridova М.

Resumo

The aim of the work was to study the properties of melts of the Na2SO4–CaSO4 system, which are best suited for practical application in metallurgy, for example, for improving the operation of industrial furnaces. In addition, information on the properties of this system is of interest for applied chemistry of molten salts, for example, for cleaning gases, metal and ceramic surfaces of structural elements. The properties of melts of binary sulfate systems, necessary for selecting application parameters, have not been studied sufficiently. The most important for practice are density, surface tension and dynamic viscosity. The work uses modern experimental research methods: maximum pressure in an argon bubble blown into the melt through a capillary to determine the density and surface tension, and the vibration method – for dynamic viscosity. The temperature and concentration ranges of measurements were 1050–1200°C and 0–60 mol. %. For the entire studied range of melt compositions, linear dependences of density and surface tension on temperature were obtained. Dynamic viscosity obeys an exponential dependence. As a result of statistical processing of the experimental data, general equations of polytherms of density, surface tension and viscosity were derived. Analysis of the experimental results showed that the values of density, surface tension and viscosity have deviations from additivity, which reflects a change in the structure of sodium sulfate – calcium sulfate melts with an increase in the concentration of CaSO4. Comparison of the obtained experimental data with those already known for binary carbonate melts indicated changes in the structure of the melts, in particular, the formation in the volume, in addition to the Na+ and Ca2+ cations and the SO42- anion, of complex anions [NaSO4]- predominantly on the surface and [Ca(SO4)]n- predominantly in the volume.

Rasplavy. 2024;(5):519-528
pages 519-528 views

Thermodynamic modeling of the processes of purification of primary aluminum from vanadium impurities

Kuandykov А., Bykov P., Chaikin V., Suyundikov М., Zhunusov А., Salina V., Kulumbaev N.

Resumo

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 (ΔGT) 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.

Rasplavy. 2024;(5):529-544
pages 529-544 views

Potentiostatic electrolysis of fluoride melts with zirconium oxide additives

Filatov А.

Resumo

Currently, the demand for zirconium-based alloys and materials is growing significantly due to their high thermal and corrosion resistance combined with mechanical strength. Existing technologies for producing zirconium and its alloys are complicated by the high temperature of the process, or labor intensity and multi-stage nature, which significantly increases the cost of the target material up to the loss of profitability of the process. Electrochemical synthesis of zirconium and its alloys in fluoride-based melts, using zirconium oxides as the main metal-containing consumable component, seems more profitable. In this work, a series of electrolysis tests were carried out to deposit Al-Zr alloy at a potential of 1.6 V on graphite and molybdenum cathodes. According to the previously obtained results, in the presence of ZrO2 in the KF-AlF3-Al2O3 melt, a plateau and a discharge peak of electroactive ions appear on the cathode branch of the voltammograms at potentials of -1.4 and -1.7 V, ZrI and ZrII, respectively. Similar responses appear on tungsten at potentials of -1.3 and -1.6 V, respectively, and in the potential region of -1.9 V there is a clear peak (Al) of electroreduction of aluminum ions. As a result of electrolysis, it was found that the graphite anode was consumed, and a fairly well-bonded deposit was formed on the cathode. Part of the cathode deposit was mechanically separated from the cathode for analysis of its chemical and phase composition. Based on the results of X-ray phase analysis, it was found that the cathode deposit mainly consists of Al3Zr and aluminum compounds with molybdenum impurities, with the composition Al12Mo, which is consistent with known ideas about the formation of intermetallic compounds during the interaction of aluminum with other metals. Electrolysis of the melt on the graphite cathode was carried out under similar conditions. Based on a microphotograph of the cathode cross section, it was found that during electrolysis, a layer of deposit containing both zirconium and aluminum was formed at the electrode-electrolyte phase boundary.

Rasplavy. 2024;(5):545-553
pages 545-553 views

Electrodeposition of ordered silicon fibers from the KI–KF–KCl–K2SiF6 melt for lithium-ion power sources

Leonova А., Leonova N., Minchenko L., Suzdaltsev А.

Resumo

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.

Rasplavy. 2024;(5):554-564
pages 554-564 views

Estimation of mixing enthalpy of the liquid Sn-Ag-Cu system at 1423 K from data on the properties of binary subsystems using geometric models of solutions

Bykov А., Oleinik К.

Resumo

The article considers the estimation of mixing enthalpy ΔНmix of the Sn-Ag-Cu ternary system melts at a temperature of 1423 K from the calorimetric data on the mixing enthalpy of binary subsystems Ag-Cu, Ag-Sn and Cu-Sn measured earlier. The geometric models by Toop, Kohler and Muggianu, where binary data is jointly processed in each case according to a specific mathematical procedure, were applied to the ΔНmix assessment. The results of calculations by these models are presented by the compositional dependences of ΔНmix of the ternary system in the form of 3D surfaces, projections of these surfaces onto the plane of the compositional triangle, as well as isotherms plotted for individual quasi-binary sections. It was found that modeling using the Kohler’s and Muggianu’s methods gives insignificantly different results, whereas the values of the mixing enthalpy of ternary compositions in the Toop’s model are noticeably more immersed into the negative (exothermic) region. As it is known from the scientific literature, the right choice of a geometric model depends on whether the ternary system under study belongs to a “symmetric” or “asymmetric” type. The shape of the available ΔНmix isotherms of binary subsystems indicates that the Sn-Ag-Cu system is “asymmetric”. The results calculated using the Toop’s model are recognized as the most correct ones, since that model is recommended in the literature for describing “asymmetric” systems. The common limitation of all geometric models, considering only binary interparticle interactions, and the advisability of extra experimental study of three-component melts formation to reveal the possible contribution of ternary interactions to the mixing enthalpy are noted.

Rasplavy. 2024;(5):565-574
pages 565-574 views

Zaikov Yuri Pavlovich – 75 years old

Rasplavy. 2024;(5):575-576
pages 575-576 views
pages 577-578 views