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Vol 124, No 10 (2023)
ЭЛЕКТРИЧЕСКИЕ И МАГНИТНЫЕ СВОЙСТВА
Magnetic Phase Transitions in Fe1 – xZnxCr2S4 Alloy: Method of Random Exchange Interaction Fields
Abstract
Abstract—
The article studies the magnetic properties of the Fe1 – xZnxCr2S4 alloy using the method of random fields of exchange interaction. The critical concentrations are determined at which a transition from the ferrimagnetic state to the spin-glass state (x = 0.66) is observed, followed by a transition to the antiferromagnetic state (x = 0.99). A magnetic phase diagram is constructed, which compares the results of calculation with experiment.
897-903
Interlayer Interaction and Coercivity of Three-Layer Films Оbtained bу Chemical Deposition
Abstract
Abstract
—The results of experimental and theoretical studies of the coercivity and the displacement field of the hysteresis loop on the thickness of the nonmagnetic interlayer in magnetic films obtained by electroless plating are presented. With the help of model calculations based on the Landau–Ginzburg equations, the exchange interactions between magnetic layers with the participation of atoms of the nonmagnetic layer are studied. The resulting expression for the displacement field describes well the exponential changes in the displacement field as a function of the interlayer thickness in structures with both magnetically soft layers and layers with significantly different values of the coercivity.
904-908
Numerical Simulation of the Spatial Distribution of the Magnetic Field in Devices for the Magnetic Sedimentation of Nanoparticles from Aqueous Media
Abstract
Abstract
—A method of magnetic sedimentation using a permanent magnets is a promising “green” technology to separate nanoparticles from water. In this work, numerical simulation of the magnetic field distribution in the devices based on combination of alternating flat permanent magnets (NdFeB) and soft magnetic steel inserts is carried out. Two types of devices with different magnetization directions of permanent magnets are considered: vertical (V) and horizontal (G). A criterion for evaluating the performance of the magnetic device R is proposed, depending on the effective volume of the water area, where the value of the product \({\text{|}}{{B}_{z}}d{{B}_{z}}{\text{/}}dz{\text{|}}\) > > 4 T2/m is realized, where Bz is the vertical component of magnetic induction. The dimensions of the permanent magnets and soft magnetic inserts along the horizontal x axis, the ratio of the thicknesses of magnetic and steel plates, and the number of plates are varied. It is shown that the maximum value R = 31% is performed using the V-type magnetic device with the thickness of the magnetic (Lx) and the steel (Ls) elements 30 mm and 2.5 mm, respectively. For G-type magnetic device maximum value R = 19% is realized at Lx = 12.5 mm and Ls = 10 mm. Magnetic devices are effective for the height of a water layer 20 mm at the given dimensions of the magnetic system.
909-915
СТРУКТУРА, ФАЗОВЫЕ ПРЕВРАЩЕНИЯ И ДИФФУЗИЯ
The Metallographic Study of High-Speed Deformation and Convergence of Thick-Walled Cylindrical Copper Shells under Explosive Loading
Abstract
Abstract—
Metallographic method investigated the process of convergence of thick-walled cylindrical copper shells under the action of an explosion. The explosion was initiated from eight points evenly spaced in a circle on the surface of the explosive surrounding the shell. At the intermediate stage of convergence, eight outliers formed on the inner surface of the shell. The convergence of the shells into the cylinder is completed by expanding and closing the emissions. The formation of outliers is explained by the occurrence of plastic (cumulative) jets at the deformation front. Jets occur when adjacent deformation projections collide. Areas of localized deformation were found inside and around the ejections, which is associated with this method of initiating an explosion. It is established that high-speed deformation of copper during the convergence of shells is accompanied by the formation of a large number of twins. There are more twins in the outer zones of the shells than in the inner ones.
916-922
Investigation of the Decomposition of Al–Sc Solid Solution during Annealing of Deformed Al–0.5% Mg–Sc Alloys
Abstract
Abstract
—The results of studies of the kinetics of solid solution decomposition during firing of fine-grained conductive alloys Al–0.5% Mg–Sc with different scandium content are presented. The alloys were obtained by induction casting, and the fine-grained microstructure was formed using equal-channel angular pressing. The kinetics of the decomposition of a solid solution has been studied using methods for measuring electrical resistivity and microhardness. The results were analyzed using the Johnson–Mel–Avrami–Kolmogorov equation. It is shown that during the firing of fine-grained alloys, the separation of Al3Sc particles along the nuclei of lattice dislocations is observed, and discontinuous precipitation of scandium in aluminum also occurs.
923-930
Effect of Mechanical Activation Time on the Density of Fine-Grained Tungsten Alloy 90W–7Ni–3Fe, Obtained by Spark Plasma Sintering
Abstract
Abstract—
The influence of the high-energy mechanical activation (HMA) time on the kinetics of solid-phase Spark Plasma Sintering (SPS) and the microstructure of a heavy tungsten alloy 90W–7Ni–3Fe has been studied. The density of the alloy 90W–7Ni–3Fe nonmonotonically, with a minimum, depends on the time of the HMA. The kinetics of the SPS of nanopowders has a two-stage character; the sintering intensity depends on the rate of Coble creep and the intensity of diffusion of W atoms in the crystal lattice of the nickel-based gama-phase.
931-938
Nanosize Dependence of the Mutual Solubility in the Solid State in the Mo–Ru Metal System
Abstract
Abstract—
The present work is devoted to constructing a method for calculating the solubility curves of molybdenum and ruthenium in the solid state in the binary Mo–Ru system with consideration of nanoscale effects. The approach is based on the thermodynamics of phase equilibria, taking into account the surface phenomena within the framework of the Gibbs thermodynamic method of separating surfaces. The surface tension is chosen as such a separating surface. The calculations of solubility were performed taking into account the dimensional dependences of the individual characteristics of metals and the parameters of interparticle interaction in the phases. A good agreement of the obtained results with the available experimental data for the macroscopic case is observed.
939-948
Evolution of the Structure and Phase Composition of a High-Entropic CoCrFeNiCu Alloy during Prolong Annealing
Abstract
Abstract
—The thermal stability of a high-entropy alloy (HEA) CoCrFeNiCu was studied during long-term annealing for 204 days in the temperature range 873–1273 K. The alloy obtained by mechanochemical alloying of metal powders in a planetary mill during 120 min in an Ar environment is a substitutional solid solution based on a high-entropy phase with a face-centered cubic structure (FCC). Upon annealing, the initial FCC phase decomposes within 1–3 days into a copper-enriched FCC1 phase and a copper-depleted FCC2 phase with similar crystal lattice parameters of 3.60 and 3.57 Å, respectively. During the entire annealing time, the intensities of the diffraction lines of theFCC1 and FCC2 phases are redistributed, the dynamics and nature of which depends on the temperature and duration of the process. After the first three days and until the end of the annealing, the HEA retains the FCC structure of the substitutional solid solution, and the unit cell parameters of the formed FCC phases remain constant with an error of 0.1% up to 204 days. The five-component matrix formed after annealing has the chemical composition Co0.23Cr0.23Fe0.23Ni0.23Cu0.08 and is stable. Also, during the entire period of annealing, an increase in the grain size is observed: at first, when an active rearrangement of the structure occurs, the size increases rapidly, then, in the period from 1 to 30 days, grain growth is limited by the diffusion of components, and at very long time intervals, grain growth is even more inhibited.
949-960
The Influence of Technological Parameters on the Structure and Properties of the Selective Laser Melting Al–Cu–Mg–Si Alloy
Abstract
Abstract
—Monolithic and bulk-structured samples of different densities were produced by means of selective laser melting on the 3D-metal printer Realizer SLM 100. An evaluation of their quality and structure characterization were carried out. Correlation of parameters of synthesis—intertrack distance and layer thickness at 200 W laser power, and structural characteristics were determined. According to the experimental results, optimal parameters of the synthesis were found for obtaining samples from AK6 alloy with dispersed structure and high mechanical properties. Correlation of the fine structure paramerers of the volume-structured samples with cubic geometry and synthesis parameters were established, types of defects that affect their mechanical properties were determined.
961-970
Formation of Chemical Short-Range Order in Equiatomic CoNiCrFeMn High-Entropy Alloy. Atomistic MD/MC Simulation
Abstract
Abstract
—The formation of short-range order in the equiatomic high-entropy alloy (HEA) CoNiCrFeMn during annealing at moderate temperatures was studied using atomistic MD/MC simulation, including the exchange of atoms in the Monte Carlo (MC) scheme and the relaxation of its positions by the molecular dynamics (MD) method. It has been found that two types of chemical short range order (CSRO) regions are formed during annealing. One of them consist mainly of Fe and Co atoms, while others are enriched by Cr with Ni and Mn atoms at their boundaries. It is shown that the formation of short-range order includes several stages, the sequence of which is determined by the value of Cr–Cr, Fe–Co and Ni–Mn interatomic interactions.
971-977
Structure and Crack Resistance of Maraging Steels under Single Loading
Abstract
Abstract
—The effect of structural parameters on the strength and crack resistance of maraging steels under single loading has been studied. It has been established that the increase in strength due to dispersion hardening with intermetallic compounds in the studied steels is determined by the titanium content and the presence of cobalt. It was shown that the change in crack resistance under single loading with increasing tempering temperature has a complex character. It has been established that, in contrast to dynamic crack resistance, the minimum level of static crack resistance characteristics of the studied steels corresponds to the maximum strength. Possible reasons for such a change in the characteristics of static and dynamic crack resistance are discussed.
978-987
Use of Eutectic Effects in the Possible Creation of PCM Memory Cells on the Basis Ag–Cu Nanoclusters
Abstract
Abstract
—An attractive direction in the development of nanoelectronics is the development of a new generation of non-volatile storage devices, namely, electric phase memory or PC-RAM (Phase Change Random Access Memory). However, there are a number of unresolved problems here, such as: the stability of the amorphous phase, high power consumption, long information recording time, etc. In order to resolve these contradictions, a new approach was proposed, which consists in the use of Ag–Cu binary alloy nanoparticles as PC-RAM cells. To this end, the molecular dynamics method was used to study the processes of structurization of nanoparticles of this alloy with a size D = 2–10 nm of various target compositions with a variation in the rate of removal of thermal energy. Criteria for the stability of the amorphous and crystalline structure were evaluated, and conclusions were drawn about the target composition and size of nanoparticles suitable for creating phase-change memory cells. It was shown that in the case of the use of nanoparticles of the binary Ag–Cu alloy, it is possible to reduce the size of one cell to 6–8 nm, reduce the time of recording information to 2.5 ns, and, for the first time, based on the eutectic approach, achieve the stability of the amorphous and crystalline structure at different rates of thermal energy removal.
988-996
Model of Fusion of Pure Metals
Abstract
Abstract
—There are model for calculating the latent heat of fusion of pure metals, included the contribution of the phonon “analogue of the Casimir force” to the melting of metals. The model makes it possible to explain the mismatch between the experimental value of the latent heat of melting and the theoretically calculated sum of the jump in the configuration and vibrational entropy during the phase transition from solid to liquid. The described approach also makes it possible to estimate the magnitude of the volume change during melting using the values of the crystallogeometric and thermodynamic parameters of the material.
997-1006
Ieffect of Ultrasonic Impact Treatment on the Microstructure and Fatigue Life of 3D-Printed Titanium Alloy Ti–6Al–4V
Abstract
Abstract
—Using a hard alloy (Co–WC) striker, ultrasonic impact treatment (UTT) of Ti–6Al–4V alloy samples obtained by electron-beam wire additive technology was carried out. Using X-ray diffraction analysis and transmission electron microscopy, it has been shown that UTT leads to the appearance of compressive macrostresses in the surface layers of the sample, elastic microdeformation in the crystal lattice of the alpha-phase, to the formation of a gradient structure from nanocrystalline at a depth of 5 μm to a submicrocrystalline structure of the alpha-phase at a depth from 15 to 40 microns.A nanocrystalline phase of titanium oxides is formed in the grains of the alpha phase. UTT leads to an increase in microhardness and fatigue life. A fractographic analysis of specimen fractures after cyclic tension in the low-cycle fatigue regime has been carried out.
1007-1014