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Vol 124, No 12 (2023)
ЭЛЕКТРИЧЕСКИЕ И МАГНИТНЫЕ СВОЙСТВА
Thermal Conductivity and Thermal Diffusivity of Iron in the Temperature Range of 300–1700 K
Abstract
Abstract—
Using the laser flash method, the thermal diffusivity (a) of carbonyl iron is measured in the temperature range of 300–1700 K with a detailed study of the critical region 980–1170 K. The initial experimental data in the field of magnetic phase transformation are processed by the scaling power law. The values of the critical indexes for thermal diffusivity (\(\gamma {\kern 1pt} ',\) γ) are obtained below and above the Curie temperature TС = 1048 ± 5 K: \(\gamma {\kern 1pt} '\) = 0.51 and γ = 0.35, which in absolute value significantly exceed the value of the characteristic critical index for the heat capacity (γ ≈ –0.1). The thermal conductivity (λ) is calculated from measured data of the thermal diffusivity. The results are compared with the known literature data, special attention is paid to the behavior of the curves a(T), λ(T) in the region of the magnetic phase transformation. A table of recommended temperature dependences for a and λ along with estimated errors has been developed.
1149-1158
Relaxation Annealing Influence on the Magnetic Properties and Magnetic Impedance of Amorphous Co-Based Wires
Abstract
Abstract—
The results of a study of the influence of the 2 hours relaxation annealing at a temperature of 620 K on the magnetoimpedance effect (MI) in amorphous Co66Fe4Nb2.5Si12.5B15 wires are presented. It was found that MI at low ac frequencies after heat treatment increases noticeably, while it changes slightly at high frequencies. Using magneto-impedance tomography, it is shown that this is due to the fact that the changes in magnetic properties caused by heat treatment are not the same in different regions of the wire. Thus, in the surface region with a thickness of about 2.5 μm, the magnetic permeability remains almost unchanged, but in the internal regions it increases significantly after annealing.
1159-1164
Effect of Titanium Diselenide Doping on the Magnetic State and Transport Properties of FeTe
Abstract
Abstract
—The iron–tellurium-based compounds Fe1.1Te(TiSe2)y doped with titanium diselenide (y = 0, 0.04, 0.08, 0.1, 0.2) have been synthesized for the first time and studied by means of x-ray diffraction, electrical resistivity and magnetization measurements. It has been shown that the addition of a small amount of titanium diselenide to single-phase iron telluride with a tetragonal crystal structure leads to the appearance of superconductivity, a decrease in the Néel temperature and contraction of the crystal lattice at y ≥ 0.04. The maximal temperature of the onset of the superconducting transition \(T_{{\text{c}}}^{{{\text{onset}}}}\) ~ 13 K is observed for a sample with the nominal composition Fe1.1Te(TiSe2)0.1. The behavior of the resistivity with temperature below Tconset is observed to depend on the current value, which may indicate superconductivity characteristic of granular superconductors.
1165-1176
Uniaxial Quadrupole Order in a Magnet With Strong Biquadratic Exchange
Abstract
Abstract—
It is shown that in a magnet with a sufficiently strong biquadratic exchange interaction (compared to bilinear exchange) and spin S > 1, the temperature transition from a disordered paramagnetic state to the ground ferromagnetic state passes through an intermediate magnetically ordered phase—uniaxial quadrupole ordering. For a magnet with spin S = 3/2, a phase diagram of magnetic states was constructed in the region of large values of the biquadratic exchange and it was studied how the sequence of two phase transitions—“paramagnetic state–quadrupole state” and “quadrupole state–ferromagnetic state”—manifests itself in the temperature behavior of the magnetic heat capacity and the initial magnetic susceptibility.
1177-1185
Modification of Fе/Gd Superlattices Crystal Structure by Hydrogenation
Abstract
Abstract—
Structural studies of multilayer magnetic nanostructures formed by alternating layers of transition (Fe) and rare earth (Gd) metals placed in a hydrogen atmosphere at a temperature of 100°C have been carried out. When hydrogen is absorbed by rare earth metals, crystalline phases GdHx arise (form), the microstructural features of which were studied by X-ray diagnostics and electron microscopy.
1186-1195
Effect of Field Annealing on Magnetic Properties of Magnetic Soft Iron–Germanium Alloys
Abstract
Abstract—
The concentration dependence of the magnetic properties of iron–germanium alloys before and after thermomagnetic treatment, which represents an annealing of alloy samples in the ferromagnetic state in a permanent or alternating magnetic field (magnetic field annealing – MFA), has been investigated. It is shown that before MFA, with an increase in the germanium content in the range of 3–30 at % Ge, the coercive force increases and the residual induction decreases. As a result of thermomagnetic treatment, in the alloy samples magnetic anisotropy is induced: the magnetic hysteresis loops become narrower, the residual induction increases, and the coercive force decreases. Thermomagnetic treatment is effective for Fe–Ge alloys with a germanium content from 6 to 18 at %, and its highest efficiency is observed at 12 at % Ge. Features of the structural state of iron–germanium alloys and their role in the formation of magnetic properties during annealing in a magnetic field are discussed.
1196-1204
Anomalous Magnetic Viscosity in (Sm,Zr)Fe11Ti Alloys with ThMn12-Type Structure
Abstract
Abstract—
Magnetic properties of the microcrystalline Sm1 – xZrxFe11Ti (x = 0, 0.1, 0.2) alloys with ThMn12-type structure were investigated. Irreversible jumps of magnetization on major hysteresis loops at low temperatures (2–4 K) were found. The jumps are random either in the magnitude of the magnetic field in which they occur or in their amplitude, and are independent of the chemical composition. There is a specific annealing temperature for each alloy, above which magnetization jumps are not observed in annealed alloys at low temperatures. The magnetic viscosity of Sm0.9Zr0.1Fe11Ti alloy annealed at 700°C was investigated at temperatures of 2–4 K. The magnetic viscosity coefficient has a discontinuity in the field of magnetization jump. This behavior is explained by thermal processes occurring during magnetization of the alloy through the magnetization jump.
1205-1210
СТРУКТУРА, ФАЗОВЫЕ ПРЕВРАЩЕНИЯ И ДИФФУЗИЯ
Structural Investigations and Rheology of Convergence of Thick-Wall Shells from Al–Mg Alloy
Abstract
Abstract
—The deformation behavior of thick-walled hollow cylindrical shells made of the AMg6 alloy (Al–6.1% Mg–0.6% Mn–0.1% Ti–0.2% Si, wt %) loaded according to an 8-point initiation scheme of an attached explosive is considered. The intensity of explosive loading was regulated by the amount of explosives. It has been established that, different scenarios for their convergence are observed depending on the intensity of the impact and the geometric characteristics of the shells. The conditions for the formation of spallation internal layers were determined, the evolution of the structure during high-speed deformation along the radius and along the length of the shells and the change in hardness along the radius of the shells were studied. X-ray photography of the dynamics of shell deformation processes was carried out at different time intervals. The speeds of movement of the outer and inner layers of the shells and the speed of their deformation for different amounts of explosives were determined.
1211-1219
Determination of the Boundaries of Region of Metastable ω-Phase in Titanium and Zirconium Alloys
Abstract
Abstract—
The concentration boundary of the formation of the ω-phase in binary titanium alloys with d-metals of 4−11 groups of 4−6 periods were studied by X-ray diffraction analysis. It is established that the ω-phase is formed in all the alloys studied, with the exception of Ti−Zr alloys. It is shown that the minimum concentration limit of the formation of the ω-phase is determined by the position of the curve of the end of the martensitic β → \(\alpha {\kern 1pt} '\)(\(\alpha {\kern 1pt} ''\)) transformation (Mf). For most of the studied titanium alloys, concentrations were determined at which the Ms and Mf points correspond to a temperature of 20°C. The conditions for the formation of the ω-phase in titanium alloys were compared with the conditions for its formation in zirconium alloys.
1220-1229
Effect of Pressure and Gravitational Field on the Distribution of Cu during the Directed Growth of a Single Crystal of the Alloy Al–0.005 wt % Cu
Abstract
Abstract—
Using quantitative X-ray spectral analysis and metallography, the distribution of copper concentration in the α-solid solution of Al and the dislocation density in single crystals of the Al alloy–0.005 wt % Cu, grown from the melt at different values of argon pressure (Ar) and the gravitational field component (gmg) directed along the surface of the crystallization front. A strong inhomogeneity in the copper concentration measured in adjacent areas of the cross-sectional surface of the crystal and its correlation with the inhomogeneity of the distribution of dislocations in single crystals of the alloy, which depends on pressure and the gravitational field component, were discovered. The mechanism of relaxation of the excess free volume of the phase transformation released in the region of the interphase boundary during crystal growth is considered.
1230-1236
Formation a Layered Dissipative Structure in the Process of Directed Growth of an MgB2 Crystal from a Melt
Abstract
Abstract—
The interaction of components during high-temperature annealing of pressed magnesium and boron powders during the production of the superconducting compound MgB2 is considered in works using standard synthesis technology and hot gas-static pressing technology. In a computer model of crystallization of a binary alloy, the influence of the diffusion of components in the region of the interphase boundary during crystal growth on the morphology of dissipative structures formed during phase transformation was studied. An analysis of the conditions and mechanism of the formation of a “layered” structure that appears during the crystallization of MgB2 from a magnesium melt in the (Mg–B) system has been carried out.
1237-1243
Model for Prediction of the Size of Austenite Grains Upon Hot Deformation of Low-Alloyed Steels Taking into Account the Evolution of the Dislocation Structure
Abstract
Abstract—
A model is proposed to describe the behavior of the average size of austenite grains and the dislocation structure of low-alloyed steels during and after hot deformation. The model takes into account the processes of recovery, dynamic recrystallization of grains and normal grain growth, as well as the strain-induced precipitation of carbonitride phases and their evolution. The calculation results are compared with the experimental data available in the literature and their satisfactory agreement is shown.
1244-1252
Atomic Structure of Ti2NiCu Alloy after Severe Plastic Deformation by High Pressure Torsion and Heat Treatment
Abstract
Abstract
—The results of a comparative analysis of the structure of Ti2NiCu alloy subjected to severe plastic deformation by high pressure torsion (HPT) and subsequent annealing are presented. The study of the structure was carried out by diffractometry of electron, X-rays and neutrons, transmission electron microscopy. It is established that an amorphous-crystalline state is formed in the alloy: nanocrystallites with a B2 lattice are present in the amorphous matrix. The analysis of diffuse maxima showed that the topological and compositional near atomic order of nanodomains with a superstructure ordered by type B2 and L21 is present in the Ti2NiCu alloy after HTP on 5 rev.
1253-1260
Thermal Physical Properties of Metals in a Quasi-Two-Phase Model
Abstract
Abstract
—The applicability of the model of a two-phase locally equilibrium region for calculating the temperature dependences of heat capacities, linear thermal expansion coefficients, and thermal diffusivities of various metals is demonstrated. It is shown that the proposed relations make it possible to describe the increase in the thermal characteristic with increasing temperature and its changes associated with the implementation of the phase transition. The possibility of extrapolating the established dependences to experimentally unexplored areas is indicated. The relative simplicity of the established relationships, a certain universality of the model in describing various solids, and the visibility of the theoretical results obtained give hope for the use of the model in engineering and technical calculations.
1261-1270
Assessment Possibility of Controlling Structure Formation by Changing the Technological Parameters LPBF Process
Abstract
Abstract
—In this paper, the possibility of creating a controlled structure by varying the parameters of laser powder bed fusion (LPBF) process on the example of austenitic stainless steels is studied. Based on the study of the structure of experimental samples, the influence of a combination of various technological parameters that make up the scanning strategy when preparing a 3D-model for the LPBF process on the processes of structure formation is shown. The possibility of forming elements with different structures within one part during its manufacture by the LPBF method by changing the technological parameters of the process that make up the scanning strategy is shown. It is noted that the use of 3D-models identical in the geometry formed, but different in the strategy of scanning with a laser beam directly in the process of laser fusion, leads to the formation of a fundamentally different structure of the created sample, since the formation of the microstructure is strongly influenced by the conditions of metal crystallization, which directly depend on the scanning strategy.
1271-1278
ПРОЧНОСТЬ И ПЛАСТИЧНОСТЬ
The Dynamic Properties of Low-Alloyed Copper Alloys with a Submicrocrystalline Structure Obtained by High-Strain-Rate Deformation
Abstract
Abstract—
The mechanical properties of alloys Cu–0.03 wt % Zr and Cu–0.10 wt % Cr with a submicrocrystalline structure formed during dynamic channel-angular pressing and subsequent annealing. The properties of the alloys were studied under shock compression conditions with a pressure of 4.7–7.0 GPa and a deformation rate of (1.3–3.2) × 105 s–1. It is shown that grain grinding from 200–400 to 0.3–1.0 microns increases the dynamic elastic limit and the dynamic yield strength of the Cu–0.03% Zr alloy by 1.9 and 1.8 times, respectively, but reduces the shear strength by 1.4 times. Subsequent annealing at 400 and 450°C can increase the characteristics of the elastic-plastic transition by 3.0 and 3.7 times, respectively, and increase the shear strength to the level of a large-crystal analog. It is determined that the dispersion of the Cu–0.10% Cr alloy structure to 1.0–5.0 microns increases not only the dynamic elastic limit and dynamic yield strength by 3.7 and 2.6 times, respectively, and the shear strength by 1.5 times, compared with its value in the coarse-grained state.
1279-1287
Structure, Phase Composition and Mechanical Properties of a High-Strength Steel with Transition Carbide η-Fe2C
Abstract
Abstract—
The influence of quenching and tempering on the structure, phase composition and mechanical properties of high-strength Fe–0.34 C steel with 1.77 wt % Si is considered. The tempering at temperatures up to 500°C has virtually no effect on the structural characteristics of packet martensite formed during quenching. At tempering temperatures in the range of 200–400°C, the precipitation of transition η-carbide occurs, which leads to an increase in the yield strength to 1490 MPa and impact toughness to 35 J/cm2. The determined temperature of the brittle-ductile transition after tempering at 200°C is about –50°C. A decrease in the impact toughness and a decrease in the proportion of ductile fracture with a decrease in the test temperature is accompanied by a transition from transgranular to intergranular fracture. The precipitation of cementite particles along the boundaries of laths and blocks is observed after tempering at 500°C. This leads to a decrease in the yield strength, while the impact toughness of the steel remains unchanged.
1288-1302
Mechanical Properties of High Entropy Alloys Based on Rare Earth Elements with Yttrium and Scandium
Abstract
Abstract—
The high-entropy alloys GdTbDyHoSc and GdTbDyHoY having equiatomic composition are considered as promising materials for magnetic cold generators. The results of the alloys structure and chemical composition investigation are presented in this paper. The solidus and liquidus temperatures of the alloys under investigation were determined by the method of differential scanning calorimetry. Based on these data, an experimental mode of thermocyclic treatment was selected. There were no signs of alloys destruction after five cycles testing for heat resistance in the following regime: 15 min exposition at 1073 K (~0.6 of the melting temperature) and subsequent quenching in room temperature water. It was found that the applied heat treatment led to an increase in the hardness of the alloys by 2–3 times and a decrease in wear resistance by 4–40 times, depending on the composition of the alloys and the number of heat treatment cycles. A significant change in the properties of alloys is associated with the formation of oxides of the REM2O3 type not only on the surface of the alloys, but also in their volume, which is due to the high chemical activity of rare earth metals (REM). The presented data will be useful for the development of modes of thermal and thermomechanical processing of various alloys.
1303-1310