Physics of Metals and Metallography (v.117, #2)

The Brown–LaBonte variation numerical method has been used to investigate the structure and energy of the Néel domain wall (DW) in a thin magnetic film of the Permalloy type. The equilibrium structure of the DW corresponds to the minimum of the total energy and to the Aharoni criterion close to unity. It has been shown that, when moving from the center of the DW, variations in the magnetization occur in an oscillating manner with a period that increases upon approaching the edge of the DW. At the edge of the DW, the period reaches a maximum value and, in this region, a sharp decrease occurs in the magnetization. In the region of the extended side tails of the DW, a larger gradient of the change in the magnetization is obtained, compared to the model of a logarithmic variation.
Keywords: thin magnetic film; Néel domain wall; effective field

Dynamic properties of ferromagnetic two-layer exchange-coupled (100) films with a combined cubic and uniaxial magnetic anisotropy of layers have been studied numerously upon the magnetization along the [100], [010], and [011] directions. The allowance for cubic anisotropy substantially affects the dependence of the frequencies of the ferromagnetic resonance on the field strength. Repeated changes in the localization of the ferromagnetic-resonance modes between the layers of the film have been found to occur with an increase in the strength of the magnetic field. At a certain relationship between the constants of the combined anisotropy for the directions [010] and [011], an increase in the field leads to a shift of the maximum of the dynamic-susceptibility distribution toward the interlayer boundary without a change in the localization of the modes.
Keywords: ferromagnetic resonance (FMR); spin-wave resonance (SWR); two-layer film; dynamic susceptibility; profiles of FMR modes

The equilibrium states and specific features of the magnetization reversal of a linear chain of magnetic moments coupled by dipole–dipole and exchange interactions have been investigated based on computer simulation. It has been revealed that, depending on the strength of the exchange interaction, the boundary between the oppositely oriented regions can have both zero and nonzero total magnetic moment. The presence of an easy-axis uniaxial anisotropy makes it possible to obtain stationary states with small domains (up to ones consisting of a single dipole). The processes of relaxation of the chain from a multidomain toward a homogeneous state have been examined.
Keywords: chain of magnetic dipoles; magnetization reversal of system; orientation of domains; transition to the homogeneous state

The Pd–5.3 at % In–0.5 at % Ru foil subjected to electrolytic hydrogenation and subsequent prolonged relaxation (for 55 000 h) has been studied by X-ray diffraction analysis. Diffraction reflections belonging to phases with different indium concentrations and palladium phases enriched in vacancies were found. Phase transformations observed in the absence of hydrogen occur mainly due to the vacancy migration; the vacancies formed during hydrogenation and remained in vacancy complexes and alloy matrix up to the moment of the study.
Keywords: hydrogen in metals; vacancies; palladium-based alloys; phase transformations; X-ray diffraction analysis

The formation, structure, and properties of the Au–Co alloys produced by severe plastic deformation under pressure by T. P. Tolmachev; V. P. Pilyugin; A. I. Ancharov; E. G. Chernyshov; A. M. Patselov (135-142).
The mechanical alloying of Au–Co mixtures, which are systems with high positive mixing enthalpy, is studied following high-pressure torsion deformation at room and cryogenic temperatures. X-ray diffractometry in synchrotron radiation and scanning microscopy are used to investigate the sequence of structural changes in the course of deforming the mixtures up to the end state of the fcc substitutional solid solution based on gold. The mechanical properties of the alloys are measured both during mixture processing and after mechanical alloying. Microfractographic studies are performed. Factors that facilitate the solubility of Co in Au, namely, increased processing pressure, cobalt concentration in a charge mixture, true strain, and temperature decreased to cryogenic level have been identified.
Keywords: Au–Co solid solution; mechanical alloying; severe plastic deformation; high-pressure torsion (shear); room-temperature and cryogenic deformation; synchrotron radiation; fractography; mechanical properties

Structural state and magnetic properties of multilayer-graphene/Fe composites by A. E. Teplykh; S. G. Bogdanov; E. G. Gerasimov; P. B. Terent’ev; A. V. Korolev; V. E. Fedorov; V. G. Makotchenko; N. G. Naumov; B. J. Campbell; A. N. Pirogov (143-150).
Results are given of measurements of X-ray and neutron diffraction, small-angle neutron scattering, and field dependences of the magnetization for nanocomposites formed by multilayer graphene and iron particles. Four samples have been investigated that differed in the content of Fe as follows: 0.75, 30, 45, and 70 wt %. The calculations of the X-ray diffraction and neutron diffraction patterns show that the size of graphene particles is about 4 nm, and the size of the iron domains of coherent scattering is no less than 50 nm. The content of the Fe particles in the composites has been estimated based on the data of the measurements of neutron diffraction, small-angle neutron scattering, and magnetization. The values of the iron concentration obtained by different methods differ quite significantly. The difference is caused by the specific character of the methods of measurements.
Keywords: nanocomposite; multilayer graphene; X-ray diffraction and neutron diffraction measurements; small-angle scattering; spontaneous magnetization

Effect of partial substitution of calcium for yttrium on the structure and properties of the Y0.9Ca0.1Ba2Cu3O6.8 superconductor by Yu. V. Blinova; L. A. Cherepanova; T. P. Krinitsina; E. I. Kuznetsova; S. V. Sudareva; S. G. Titova; S. V. Pryanichnikov; M. V. Degtyarev; E. P. Romanov (151-159).
The crystal structure of the high-temperature Y1–x Ca x Ba2Cu3O6.8 superconductor has been studied in a temperature range of 80–300 K using low-temperature X-ray diffraction analysis; its microstructure has been studied by scanning and transmission electron microscopy. Changes of the bond length in the structure of principal phase and precipitation topology of impurity phases and their compositions have been analyzed. An addition of calcium was shown to increase the environmental tolerance of the principal Y123 phase and its microhardness and ensures the low unchanged coefficient of thermal expansion. All of the facts indicate that the material can be used to manufacture composite superconducting articles.
Keywords: high-temperature superconductor; coefficient of thermal expansion; structure

Precipitation-hardening stainless steels with a shape-memory effect by V. V. Sagaradze; S. V. Afanasiev; E. G. Volkova; V. A. Zavalishin (160-166).
The possibility of obtaining the shape-memory effect as a result of the γ → ε → γ transformations in aging stainless steels strengthened by VC carbides has been investigated. Regimes are given for strengthening aging (at 650 and 720°C) for stainless steels that predominantly contain (in wt %) 0.06–0.45C, 1–2V, 2–5Si, 9 and 13–14Cr. The values of reversible deformation e (amount of shape-memory effect) determined after heating to 400°C in samples preliminarily deformed to 3.5–4% vary from 0.15 to 2.7%, depending on the composition of the steels and regimes of stabilizing and destabilizing aging.
Keywords: shape-memory effect (SME); aging stainless steels; vanadium carbide VC; martensitic transformation; ε phase; electron microscopy

Metallographic study of articles of the Kamensk iron foundry and iron works produced in the 18th–20th centuries by V. M. Schastlivtsev; B. A. Gizhevski; Yu. V. Khlebnikova; S. V. Naumov; L. Yu. Egorova (167-177).
Results have been presented for studies of the microstructure and chemical composition of a number of articles made of iron and cast iron at the Kamensk plant, which cover the period from the start of the production of iron on the territory of the city of Kamensk-Ural’skii at the turn of the 17th–18th centuries to the beginning of the 20th century. Differences in the composition of the Kamensk cast iron and modern grades of foundry cast iron have been established. Possible sources of technological difficulties and production waste at the Kamensk plant have been revealed. The potential of metallographic studies for the attribution of historical articles made of ferrous metals are shown.
Keywords: cast iron; iron; chemical composition; technological modernization; metallography

Methods of X-ray diffraction, differential thermal analysis, and measurements of the dynamic magnetic susceptibility have been used to investigate the sequence of phase transformations upon the mechanical alloying of a mixture of powders of the initial components of the composition (Fe0.93Cr.07)75C25. It has been shown that, at later stages of mechanical alloying, the phase composition is determined by the conditions of the dynamic equilibrium between the crystalline and amorphous phases. A change in the conditions of mechanical alloying leads to a shift in this equilibrium and to a change in the phase composition of the alloy. A comparison of carbide formation in the Fe–C system upon the mechanosynthesis, tempering of martensite, the saturation of iron with carbon from the gaseous medium, the quenching of the melt, and the sputtering deposition of films has been performed. Some general regularities have been established, from which it follows that an important role in phase formation upon the mechanosynthesis, just as in other abovementioned processes, is played by the thermally activated phenomena.
Keywords: phase transformations; mechanical alloying; amorphous alloys; structure; metallic alloys; cementite; iron carbides

Structure, phase composition, and strengthening of cast Al–Ca–Mg–Sc alloys by N. A. Belov; E. A. Naumova; T. A. Bazlova; E. V. Alekseeva (188-194).
The structure and phase composition of Al–Ca–Mg–Sc alloys containing 0.3 wt % Sc, up to 10 wt % Ca, and up to 10 wt % Mg have been investigated in the cast state and state after heat treatment. It has been shown that only binary phases Al4Ca, Al3Sc, and Al3Mg2 can be in equilibrium with the aluminum solid solution. It has been found that the maximum strengthening effect caused by the precipitation of Al3Sc nanoparticles for all investigated alloys is attained after annealing at 300–350°C.
Keywords: Al–Ca–Mg–Sc system; Al3Sc nanoparticles; phase composition; microstructure; eutectic; thermal treatment; hardening

The macro- and microstructures and the distribution of elements and of the values of the microhardness and contact modulus of elasticity along the height and width of the weld metal and heat-affected zone of austenitic corrosion-resistant 12Kh18N10T steel (Russian analog of AISI 321) and titanium alloy VT1-0 (Grade 2) with an intermediate copper insert have been studied after laser welding under different conditions. The structural inhomogeneity of the joint obtained according to one of the regimes selected has been shown: the material of the welded joint represents a supersaturated solid solution of Fe, Ni, Cr, and Ti in the crystal lattice of copper with a uniformly distributed particles of intermetallic compounds Ti(Fe,Cr) and TiCu3. At the boundaries with steel and with the titanium alloy, diffusion zones with thicknesses of 0.1–0.2 mm are formed that represent supersaturated solid solutions based on iron and titanium. The strength of such a joint was 474 MPa, which corresponds to the level of strength of the titanium alloy. A numerical simulation of the mechanical behavior of welded joints upon the elastic tension–compression has been performed taking into account their structural state, which makes it possible to determine the amplitude values of the deformations of the material of the weld.
Keywords: laser welding; diffusion zone; weld; macrostructure; microstructure; intermetallic compound; supersaturated solid solution; microhardness; contact modulus of elasticity; deformation; finite-element simulation