Russian Metallurgy (Metally)最新文献

Abstract—The structures of model analogs of salt melts containing neodymium complexes are subjected to ab initio studies. The importance of this work is mainly determined by the need to develop methods and technologies for recycling electronic and magnetic materials, which are a secondary source of rare earth metals. Quantum-chemical calculations, in turn, are a powerful tool for studying the structural features of model analogs of real high-temperature salt melts. The calculations are performed by the Hartree–Fock and density functional theory methods using the quantum-chemical Firefly 8.20 software package. An approach is proposed to calculate the interaction energies in a three-component model system consisting of a neodymium complex, an outer-sphere (OS) cation shell, and the remaining part of the cluster. The energies of interaction of the neodymium complex with the system fragments are determined. The influence of the number of OS cations on the calculated interaction energies has been studied, and the compositions of the most stable particles consisting of neodymium complex + OS shell have been determined. The data obtained using quantum-chemical calculations are compared with the results available in the world scientific literature, including the results of direct spectroscopic studies of molten salts containing neodymium complexes. The calculated interatomic distances Nd–X (X = F, Cl) are shown to agree well with the available experimental data. Raman spectra are calculated for 18MCl + M₃NdCl₆ (M = Na, K, Rb, Cs) model systems, and the calculated and experimental frequencies of the most intense spectral line are shown to be in good agreement. The results obtained allow us to assert that the model systems studied in this work can be used as the minimum possible ones for studying the structures of molten salts using quantum-chemical methods.

The effect of hot plastic deformation on the structure and properties of new corrosion-resistant nitrogen-bearing 08Kh17N2AF ferritic–martensitic steel has been investigated. Research data for wedgelike specimens have shown that rolling with a steel reduction up to 70% in the temperature interval 800–1100°C doles not result in specimen failure. Specimens deform uniformly both in the transverse and in the longitudinal directions without cracking on the surface and in the volume. The hardness of 08Kh17N2AF steel reaches a maximum, 41–43 HRC, after rolling in the temperature range 850–1100°C with a reduction of 30–70%. It has been found that 03Kh17N2AF steel rolled in the temperature interval 1000–900°C and cooled in air offers the best combination of strength (HRC = 40, rupture strength σ_r = 1280 MPa, yield strength σ_0.2 = 1010 MPa), ductility (δ = 17.9%, ψ = 58.8%), and impact toughness (KCU^+20°C = 0.85 MJ/m², KCU^–70°C = 0.56 MJ/m²). Such a combination of mechanical properties is due to the formation of a fine-grained structure consisting of lath martensite (66%), ferrite (20%), and retained austenite (14%) with thin ferrite and austenite lamellas between martensite laths. A pilot batch of parent sheets and malleable billets made of 08Kh17N2AF steel that are promising for producing high-load products to be used in corrosive media and at low (down to –70°C) temperatures has been prepared.

The technological features of friction stir welding of the butt joints of AlSi10Mg alloy powder plates produced by selective laser melting are investigated. The AlSi10Mg alloy plates are grown by selective laser melting at an angle of 90° to a build platform. The ultimate tensile strength of the welded joints of the plates grown by selective laser melting is 274–306 MPa, and the bending angle of the plates is 69°–85°. The fracture of the welded joints occurs along the mixing zone metal. The following two types of porosity are found in the microstructure of the base metal: flattened pores along the boundary of visible melt baths and spherical pores. No porosity is found in the mixing zone metal.

Abstract—The existing methods for controlling residual stresses are analyzed. A quantitative estimation of the stresses in a titanium alloy sample using an eddy current method is experimentally tested. The design of the developed technological equipment for controlled loading of samples is described, and the choice of control conditions is justified.

The influence of silver additives in an amount of 0.2 and 0.5 wt % on the structure and mechanical properties of 03Kh17N10M2 steel sheets 1 μm thick has been studied. The steel has been obtained by means of argon arc remelting followed by homogenization annealing and hot longitudinal rolling. It has been found that when the silver content rises from 0 to 0.5 wt %, the strength parameters of the steel somewhat decline: σ_0.2 and σ_r drop from 560 to 510 MPa and from 760 to 710 MPa, respectively, and the microhardness decreases from 274 to 250 HV. However, these values remain within the ASTM A240 requirements. In both cases, the fracture surface represents an ensemble of self-similar tough fracture pores (cups). The new type of steel (with a silver content of up to 0.5 wt %) may be efficient in the production of products with pronounced antibacterial properties.

Titanium alloy VT6 samples fabricated by selective laser melting are studied. The influence of the annealing temperature on the residual stresses, texture formation, and mechanical properties of the titanium alloy samples grown in different directions has been determined.

Composite material specimens are fabricated by reaction casting by mixing titanium particles to form Al₃Ti intermetallic phases. Dry sliding friction tests are carried out according to the scheme of end loading of a fixed sleeve (grade 45 steel) on a rotating disk (specimen) at sliding speeds of 0.25–0.75 m/s and loads of 0.5–3.5 MPa. Wear intensity maps, which determine friction regimes during a test, are constructed. The boundaries and conditions for changing the friction regimes are shown.

Abstract—The necessity of restructuring the existing steelmaking scheme is justified not only under the pressure of environmental decarbonization requirements, but also under the need to bring steelmaking technologies in line with the level of modern science. The scientific basis of new reduction technologies is shown to be the electronic theory of metal oxidation/reduction, which allows one to consider the thermodynamic and kinetic conditions of processes with partial or complete replacement of fossil carbon-containing reducing agents with hydrogen from a unified standpoint. A comparison of two well-known technologies with zero carbon dioxide emission, namely, iron reduction with “green” hydrogen or iron production by electrolysis of ore, shows a multiple advantage of electrolysis in terms of energy consumption and more favorable kinetic conditions for its implementation. It is concluded that, when an industry development strategy is designed, priority should be given to the electrolysis of ore rather than to the production and use of green hydrogen. The use of hydrogen as a reducing agent can be justified for selective iron extraction from complex ores in plants, such as plasma mine furnaces, plasma reactors, and suspended-slurry reduction reactors, where nitriding would also take place to transform soft iron into steel along with reduction.

Abstract—Since the demand for renewable energy sources is still increasing, the main research in the battery industry is focused on the development of safe and high-capacity energy storage systems capable of sustaining high current loads and made of inexpensive and readily available materials. An aluminum-ion battery (AIB) using metallic aluminum as the anode, carbon materials as the cathode, and chloroaluminate ionic liquids as the electrolyte is considered to be among the most promising systems. A low-temperature chloroaluminate melt based on triethylamine hydrochloride (Et₃NHCl) is one of inexpensive electrolytes for AIB. This melt can reversibly precipitate/dissolve metallic aluminum due to the presence of the ({text{A}}{{{text{l}}}_{{text{2}}}}{text{Cl}}_{7}^{ - }) ion in it. However, the diffusion of ({text{A}}{{{text{l}}}_{{text{2}}}}{text{Cl}}_{7}^{ - }) ions in the Et₃NHCl–AlCl₃ system has not been studied previously. In this work, the concentration dependences of the diffusion coefficients of the ({text{A}}{{{text{l}}}_{{text{2}}}}{text{Cl}}_{7}^{ - }) anion are studied using chronopotentiometry in the concentration range N = 1.3–1.95 (where N is the molar ratio of aluminum chloride to organic salt). The diffusion coefficients are shown to increase with an increase in the aluminum chloride content in the melt: from 1.71 × 10^–7 (N = 1.3) to 4.50 × 10^–7 cm² s^–1 (N = 1.95). A similar behavior can be caused by a decrease in the viscosity of the melts with an increase in the ({text{A}}{{{text{l}}}_{{text{2}}}}{text{Cl}}_{7}^{ - }) concentration. The obtained results show that Et₃NHCl–AlCl₃ with N = 1.95 is the most suitable electrolyte for operating in AIB. In addition, the electrochemical reduction of the ({text{A}}{{{text{l}}}_{{text{2}}}}{text{Cl}}_{7}^{ - }) ion on the aluminum electrode surface is found to be complicated by the nucleation process, which has the lowest overvoltage at N = 1.95.

Abstract—The results of a computation-experimental estimation of the resistance of the welding zone during electrocontact welding (ECW) of a metal tape through an intermediate layer are presented. Characteristic resistance zones are determined, and the stages of joint formation and the state of resistance during ECW are considered. The influence of the compressive force on the resistance of the joint zone, the welding current, and the heat released in the welding zone at each contact site is analyzed, and dependences for calculating these quantities are presented with allowance for shunting and heating of the materials to be joined. The optimum compressive forces at each ECW stage are determined. Recommendations are given for adjusting the welding current during transitions to the next welding stages.