Physics of Metals and Metallography (v.112, #3)

The dynamics of a 180° domain wall in a magnet with two-dimensional inhomogeneities of the parameters of magnetic anisotropy and the conditions of excitation of nonlinear magnetization waves have been investigated using numerical methods. Three types of localized magnetic inhomogeneities that appear in the region of anisotropy inhomogeneities have been revealed, namely, a pulson, a pulson transforming into a 2D soliton, and a 2D soliton. Regions of the values of the parameters that describe the magnetic-anisotropy inhomogeneities, which determine the existence of each of these inhomogeneities, have been found.
Keywords: dynamics; domain wall; magnetic inhomogeneities; soliton; pulson

Magnetocrystalline anisotropy, magnetization curves, and domain structure of FeB single crystals by O. V. Zhdanova; M. B. Lyakhova; Yu. G. Pastushenkov (224-230).
Single crystals of an orthorhombic compound FeB have been synthesized. Based on the data of magnetic measurements and X-ray diffraction analysis, it has been shown that two mutually perpendicular preferred magnetization axes exist in the orthorhombic single crystals of FeB: the easy axis (EA) corresponds to the crystallographic axis [010], and the hard axis (HA), to the [100] axis. The function of the energy of magnetocrystalline anisotropy (MCA) of the orthorhombic magnets has been analyzed for extrema. Orientations of the EAs and HAs have been determined. It has been established that in the orthorhombic magnets there is always realized a single type of MCA: two preferred mutually perpendicular axes always exist in the crystals, one of which is an EA, and the other is an HA. Expressions for the anisotropy fields of orthorhombic magnets have been obtained. The constants of MCA of the orthorhombic compound FeB have been calculated to be K 1 * ≈ 4 × 105 J/m3 and K 2 * 7×104 J/m3. The domain structure on the planes (100), (010), and (001) of the FeB single crystals has been studied. It has been shown that the main volume of the sample is occupied by stripe domains ∼40 μm wide with the walls oriented along (100) crystallographic planes. It has been found that the structure of closure domains on the plane (010) of the FeB single crystals has some specific features, namely, there exists a preferred direction in the structure for the orientation of the boundaries of the main domains, and the closure domains have the shape of regular rhombs. A model of the domain structure of FeB single crystals is suggested.
Keywords: magnetic anisotropy; magnetization curve; domain structure; orthorhombic ferromagnet

Effect of an electrical insulating coating on the efficiency of laser treatment of grain-oriented electrical steel by L. S. Karenina; Yu. N. Dragoshanskii; R. B. Puzhevich; G. S. Korzunin (231-236).
Effect of an electrical insulating coating on the efficiency of laser treatment of an electrical grain-oriented steel has been studied. The similarity and distinctions of the mechanisms of the action of laser treatment and electrical insulating coating on the magnetic losses in steel have been analyzed. It has been shown, both on separate samples and on commercial parties that the coating reduces the efficiency of laser treatment and that the lower the tensile stresses produced by the coating in the metal, the more pronounced the effect of laser treatment. The results obtained also show the absence of the additivity upon the combined action of laser treatment and electrical insulating coating on the metal.
Keywords: grain-oriented electrical steel; laser treatment; electrical insulating coating; magnetic losses; tensile stresses; domain structure

Phase transformations in commercial alloys 1424, V-1469, and 1441 during long-term low-temperature exposures by E. A. Lukina; A. A. Alekseev; V. V. Antipov; L. B. Khokhlatova; P. L. Zhuravlev (237-244).
The problem of changes in properties, which are caused by long-term low-temperature exposures, is typical of all Al-Li alloys. In this study, electron transmission microscopy and X-ray diffraction were used to investigate the structure of aged sheets of commercial Al-Mg-Li alloys 1424, 1441, and V-1469, which were subjected to additional long-term low-temperature exposures (LLTEs) at 85°C for up to 7500 h, at 85 and 130°C for up to 2000 h, and at 125 and 150°C for up to 2000 h, respectively. For structural studies, a JEM-200CX electron microscope and a D/MAX 2500 X-ray diffractometer were used. The X-ray diffraction studies included the phase analysis and special measurements of reflection intensities in a 2θ angular range from 1° to 25°, which allowed us to investigate an additional decomposition at 85°C (which yields disperse particles) using small-angle X-ray scattering effects. In the 1424 and 1441 alloys, the structural changes during LLTEs are determined by the specific features of the δ′ phase, whereas the structural changes in the V-1469 alloy after artificial aging and subsequent LLTEs are due to the precipitation of the Ω′ phase.
Keywords: phase transformations; low-temperature heating; Al-Li alloys; δ′ phase; Ω′ phase; aging; lattice parameter; X-ray diffraction analysis (XRD); transmission electron microscopy (TEM)

Formation of boron solid solution in Fe-Ni invar upon severe plastic deformation by V. A. Shabashov; A. V. Litvinov; N. V. Kataeva; K. A. Lyashkov; S. I. Novikov; S. G. Titova (245-255).
Mössbauer spectroscopy, X-ray diffraction, electron microscopy, and magnetic susceptibility measurements have been used to study the process of mechanical synthesis of the solid solution of boron in the matrix of an Fe-Ni alloy. The internal effective field, the Curie temperature, and the lattice parameter of the Fe-Ni austenite were found to increase after severe plastic deformation in Bridgman anvils, which is related to the incorporation of boron into the matrix and the formation of a crystalline supersaturated solid solution coexisting with metastable borides.
Keywords: Fe-Ni; boron; mehanical alloying; deformation; Mössbauer spectroscopy

Based on the recently proposed model of grain-boundary diffusion, the available research data on grain-boundary diffusion of Co in W, and on emission Mössbauer studies of grain boundaries in polycrystalline W have been analyzed in detail. Using joint processing of primary data for tracer analysis and Mössbauer studies, all the parameters of grain-boundary diffusion of Co in W have been determined: the coefficient of grain-boundary segregation, coefficient of grain-boundary diffusion, and the diffusion width of the grain boundary.
Keywords: grain-boundary diffusion; layer-by-layer tracer analysis; Mössbauer spectroscopy

Structure of a metastable austenitic invar alloy Fe-32% Ni preliminarily quenched for martensite and subjected to α → γ transformation using slow heating to various temperatures (430–500°C) with the formation of variously oriented nanocrystalline lamellar austenite, which was subjected to an additional annealing at 280°C (below the calculated temperature of ordering of the γ phase), has been studied electron-microscopically. An electron diffraction analysis revealed the presence of an L10 superstructure in the disperse nickel-enriched nanocrystalline γ phase both after annealing at 280°C and in the unannealed alloy immediately after α → γ transformation upon slow heating to 430°C.
Keywords: Fe-32% Ni alloy; electron-microscopic method; structure investigations; α → γ transformation; L10 superstructure

The influence of a heat treatment on the behavior of the volume effect and the degree of shape recovery upon the martensitic transformation for the Fe-24 at % Pt alloy has been studied. It has been found that an increase in the time of annealing at 650°C from 0 to 300 min leads to a continuous decrease in ΔV/V from 1.26% in the quenched condition to 0.987% for τ = 300 min. The characteristic temperatures of the martensitic transformation decrease, and the hysteresis passes through a minimum. The shape memory effect in the heat-treated samples after τ = 40 min achieves 100%.
Keywords: martensitic transformation; volume effect; degree of shape recovery; temperature hysteresis; ordering

Structure and phase transformations in an elinvar alloy after various regimes of heat treatment by V. A. Skudnov; S. V. Kharitonov; L. A. Oshurina; A. A. Khlybov; R. A. Blyakevichus (283-289).
The microstructure, phase composition, and mechanical properties of the alloy 44NKhTYu have been studied using metallography, X-ray diffraction, and acoustic testing. The main peculiarities of the formation of intermetallic phases and their effect on the mechanical properties of the alloy have been determined.
Keywords: elinvar alloy 44NKhTYu; heat-treatment regimes; microstructure; X-ray diffraction analysis; acoustic testing

The effect of frictional heating (whose intensity was varied at the expense of changes in the sliding velocity from 0.35 to 9.00 m/s) on the rate of wear, friction coefficient, friction thermopower, structure, and microhardness of the Ti49.4Ni50.6 alloy in a microcrystalline (MC) state with grains 20–30 μm in size and in a submicrocrystalline (SMC) state with grains 300 nm in size has been investigated. The tribological tests were conducted under the conditions of dry sliding friction in air using the finger-disk (made of steel Kh12M, hardness HRC = 63) scheme at a normal load of 98 N. Due to the frictional heating, the temperature in the surface layer 0.5 mm thick of the samples changed from 150–200 (at a sliding velocity of 0.35 m/s) to 1100°C (at a velocity of 9 m/s). The alloy structure has been studied with the help of metallographic and electronmicroscopic (scanning and transmission microscopy) methods. It has been shown that the rate of wear of the titanium nickelide in the MC and SMC structural states is more than an order of magnitude lower than in the 12Kh18N9 steel and several times less than in the 40Kh13 steel. The fracture of the friction surface of the titanium nickelide occurs predominantly by the fatigue or oxidation-fatigue mechanisms, which are characterized by a relatively low wear rate, whereas the 40Kh13 and 12Kh18N9 steels show a tendency to intense thermal adhesive wear (seizure) at velocities higher than 0.35 m/s. It has been shown by the electron-microscopic investigation that nanocrystalline structures consisting of crystals of the B2 phase, oxides of the TiO2 type, and some amount of martensite B19′ are formed in the process of friction in the surface layer of the titanium nickelide. It has been concluded that an enhanced wear resistance of the titanium nickelide is caused by the high heat resistance (strength) and high fracture toughness of the nanocrystalline B2 phase and by the presence of high-strength thermostable oxides of the TiO2 type formed upon friction.
Keywords: Ti49.4Ni50.6 alloy; frictional heating; tribological properties; structural transformations upon wear

The technique and the results of studying slightly etched fracture surfaces of samples of carbon steel in structural states with a large fraction of carbides (pearlite, bainite, tempered martensite) are given. The technique presented made it possible to reveal, directly on the facets of brittle transcrystalline and intercrystalline fracture, elements of a microscopic and fine macroscopic structure that have undergone fracture.
Keywords: carbon steel; brittle fracture; etching; fractography

The structure and magnetic properties of a heat-resistant nickel-base alloy after a high-temperature deformation by N. N. Stepanova; D. I. Davydov; A. P. Nichipuruk; M. B. Rigmant; N. V. Kazantseva; N. I. Vinogradova; A. N. Pirogov; E. P. Romanov (309-317).
The structure of a turbine blade made of the ChS-70V alloy has been studied after operation in an experimental regime at 880°C. A considerable change in the structural state of the alloy indicates the presence of an extremely high level of stresses in the material. During the operation, the magnetic susceptibility of the alloy increases by two orders of magnitude. The possible structure objects responsible for a change in the magnetic susceptibility are the complexes of superstructure intrinsic stacking faults inside the intermetallic phase.
Keywords: structure; deformation; magnetic properties; stacking faults; heat-resistant alloys