Physics of Metals and Metallography (v.111, #1)
Structural transformations, distribution of nonequilibrium vacancies, and anomalous diffusion in plastically deformed metals and alloys upon mechanical alloying by L. S. Vasil’ev; I. L. Lomaev (1-12).
Processes of structural transformations leading to the generation of fluxes of nonequilibrium point defects and anomalously high rates of diffusion of substitutional impurities in nanostructured metallic systems upon mechanical alloying have been investigated. The basic contribution to the anomalous acceleration of diffusional mass transfer was shown to come from the nonequilibrium vacancies generated by processes of the deformation-induced migration of intercrystallite boundaries. The influence of interstitial atoms on the diffusion and processes of recrystallization was found to be negligible. The specific features of the formation of strongly supersaturated substitutional solid solutions upon severe plastic deformation of metals and alloys have been examined.
Keywords: plastic deformation; nanostructured metals; diffusion
Study of the thermodynamic characteristics of gold nanoclusters using a Gupta many-body potential by N. Yu. Sdobnyakov; P. V. Komarov; D. N. Sokolov; V. M. Samsonov (13-20).
The Monte Carlo method has been employed to investigate the hysteresis of the process of melting and crystallization of gold nanoclusters using a many-body Gupta potential. The size dependence of the effective specific total surface energy of gold nanoclusters has been calculated and analyzed based on the Gibbs surface phase method.
Keywords: hysteresis of melting and crystallization of gold nanoparticles; Gupta potential; effective specific total surface energy
Effect of the phosphate component of electrical insulating coating on the magnetic losses in grain-oriented electrical steel by L. S. Karenina; G. S. Korzunin; R. B. Puzhevich (21-24).
It is shown that one of the main methods improving quality of a grain-oriented electrical sheet steel (GOES) is the deposition of an electrical insulating coating (EIC) on its surface, which produces elastic tensile stresses in the metal. The EIC represents a composite consisting of a glass film and a phosphate coating deposited on it. Investigations performed in this direction are reviewed. A complex of the industrial experiments has been carried out, which were directed to studying the effect of both the insulating coating as a whole and, separately, its phosphate component (PC) on the level of magnetic losses. The values of elastic tensile stresses produced in the metal by the EIC and PC are presented. This work has been performed under the conditions of the OOO VIZ-stal’ (Verkneisetsk Factory).
Keywords: grain-oriented electrical sheet steel; electrical insulating coating; ground layer; phosphate component; magnetic losses; domain structure; elastic tensile stresses
Dynamics of the evolution of a magnetization-reversal nucleus in orthorhombic antiferromagnets with a weak ferromagnetism by M. A. Shamsutdinov; A. P. Tankeyev; I. R. Kayumov (25-37).
Dynamics of a two-dimensional nucleus of magnetization reversal in a magnetic field in an orthorhombic antiferromagnet with a weak ferromagnetism has been investigated analytically and numerically. It is shown that along the nucleus of the stable phase inside the metastable phase there can propagate both slow periodic and rapid periodic and solitary waves of magnetization. It is shown that the wave that describes the intergrowth of a domain of the reverse magnetization can have a velocity greater than the maximum velocity of the stationary motion of the domain wall, equal to the minimum phase velocity of spin waves.
Keywords: weak ferromagnet; magnetization-reversal nucleus; structure; dynamics; solitons
Mössbauer study of the process of the room-temperature aging of the alloy Cu79Ni14Fe7 by A. V. Pyataev; R. A. Manapov (38-44).
Mössbauer spectroscopy was used to investigate the initial stage of the phase separation in the quasi-binary system Cu79Ni14Fe7 and the subsequent transformation of the alloy structures as a result of prolonged aging at room temperature. For describing the Mössbauer spectra of ferromagnetic particles, which appear upon the spinodal decomposition in a paramagnetic matrix, a model was proposed and approved, which uses particle-size distribution in the approximation of the generalized Lifshitz-Slezov-Wagner (LSW) model and of the linear decrease of the hyperfine field at the 57Fe nuclei in the near-surface layers of spherical particles.
Keywords: alloys; spinodal decomposition; Mössbauer effect
Study of the interaction of mechanochemically produced cu-in solid solutions with liquid gallium and of the structure of metallic cements on their basis by T. F. Grigor’eva; S. A. Kovaleva; A. P. Barinova; P. A. Vityaz’; N. Z. Lyakhov (45-52).
Methods of atomic-force and scanning electron microscopy and X-ray diffraction and electron microprobe analysis were used to study metallic cements formed upon the interaction of Cu-In mechanocomposites with different contents of indium. It has been established that an increase in the amount of indium in the mechanocomposite, which represents mainly a solid solution of indium in copper, leads to a decrease in the sizes of particles of the basic intermetallic compound CuGa2 in the material obtained. After a certain induction period, indium forms a solid solution with gallium in the form of separate crystallites and nanodimensional films on the faces of CuGa2 crystals.
Keywords: metallic cements; mechanocomposites; microstructure of alloys
Laser sintering of Fe-Ni nanocomposites by E. V. Kharanzhevskiy; M. D. Krivilyov (53-61).
The laser sintering of powders is one of new technologies of producing surface coatings from nanostructural materials. In this work, we used methods of transmission and scanning electron microscopy, X-ray diffraction analysis, and X-ray photoelectron spectroscopy to study the structure of layers synthesized using laser sintering of an ultradispersed powder consisting of Fe-Ni nanocomposites. For explaining the specific characteristics of the structure that was formed as a result of high-energy laser action, we carried out a mathematical simulation of the processes of heat transfer with the application of the model of a two-phase (mushy) zone. The coatings synthesized possess a multilevel system of connected pores and can be used in catalytic reactions and hydrogen power engineering.
Keywords: laser sintering; SLS; Fe-Ni nanocomposites; mechanoactivation; mathematical simulation
Effect of high-temperature annealing on the microstructure and mechanical properties of ferritic-pearlitic steel 10G2FT subjected to equal-channel angular pressing by E. G. Astafurova; G. G. Zakharova; E. V. Naydenkin; G. I. Raab; S. V. Dobatkin (62-71).
Results are given of the investigation of mechanical properties, microstructure, and phase composition of low-carbon ferritic-pearlitic steel 10G2FT (Fe-1.12Mn-0.08V-0.07Ti-0.1C) after equal-channel angular pressing and subsequent high-temperature annealing at temperatures of 500–700°C. It has been shown that the predominantly submicrocrystalline structure formed during the equal-channel angular pressing possesses high thermostability up to a temperature of 500°C. The contribution of age hardening to the strengthening of steel 10G2FT during the equal-channel angular pressing and to the stabilization of the submicrocrystalline structure to high annealing temperatures is discussed.
Keywords: equal-channel angular pressing; low-carbon steels; ferrite; pearlite; thermostability of submicroc-rystalline structures
Effect of severe plastic deformation on the formation of the nanocrystalline structure and the aging of the multicomponent aluminum-lithium alloy with small additions of Sc and Mg by L. I. Kaigorodova; V. G. Pushin; D. Yu. Rasposienko; V. P. Pilyugin (72-79).
Effect of severe plastic deformation and subsequent low-temperature annealing on the structural and phase transformations, which are realized in the alloy 1450 on the base of the Al-Li-Cu-Zr system with additives of Sc and Mg has been studied by electron microscopy. The possibility of obtaining a nanocrystalline recrystallized structure in the alloy investigated has been established. It has been shown that its uniformity and dispersiveness depend on the degree of deformation and on the regime of annealing and are determined by the density distribution of particles that are precipitated upon the decomposition of the supersaturated solid solution. The transition of the alloy from microcrystalline to submicrocrystalline or nanocrystalline state changes its phase composition, morphology, and mechanism of nucleation of the precipitated phases and makes it possible to minimize structural factors that exert negative effect on the alloy plasticity.
Evolution of the microstructure and microstresses in the 40Kh4G18F2 steel upon carbide aging by V. V. Sagaradze; B. N. Goshchitskii; E. G. Volkova; V. I. Voronin; I. F. Berger; A. I. Uvarov (80-90).
Structural mechanism of aging of the 40Kh4G18F2 steel at 600 and 700°C (precipitation of clusters and VC carbide particles) has been clarified, and its effect on the magnitude of the elastic microdeformation of the lattice of an austenitic matrix and, consequently, on the magnitude of microstresses, has been analyzed.
Keywords: manganese austenite; carbide strengthening; electron microscopy; neutron diffraction analysis; microdistortions; microstresses
Electron-microscopic examination of microstructural changes in structural martensitic steel after low-cyclic fatigue tests by T. V. Eterashvili (91-94).
Microstructural changes in a structural martensitic steel upon low-cyclic fatigue (LCF) deformation have been investigated. The micromechanics of plastic deformation and accompanying effects have been studied at the scale of martensite laths and packets with the aid of transmission electron microscopy (TEM). It has been shown that with increasing LCF deformation, changes in both the morphology and the internal structure of martensite occur. The changes are manifested in the form of a refinement of the structural units of martensite. It has been revealed that in the limits of a packet the fatigue deformation occurs inhomogeneously. However, the laths of the same orientation are deformed equally and almost simultaneously. The influence of the dimensions of former austenite grains and orientation of packets on the LCF process has been considered. The mechanics of the fatigue plastic deformation on the nano-, meso-, and microlevels and the processes that accompany this deformation have been studied.
Keywords: fatigue; steel; martensite; deformation; packet; microstructure
Structural features of the behavior of a high-carbon pearlitic steel upon cyclic loading by A. V. Makarov; R. A. Savrai; V. M. Schastlivtsev; T. I. Tabatchikova; I. L. Yakovleva; L. Yu. Egorova (95-109).
The structural evolution upon high-cycle fatigue (tension with the magnitude of stress in a cycle below the macroscopic yield stress) of the hypereutectoid steel U10 (1.03 wt % C), in which pearlite of different morphology (fine-lamellar, coarse-lamellar, and partially spheroidized pearlite) was formed, has been investigated by scanning and transmission electron microscopy. Based on the fractographic analysis, features of fracture of these structural states have been considered. At a significant distance (10 mm) from the fatigue fracture, features of structural transformations caused by cyclic loading have been revealed. It has been shown that upon high-cycle fatigue in the steel U10 with structures of lamellar and partially spheroidized pearlite, substantial structural changes occur, namely, fragmentation and partial dissolution of cementite plates, and in fine pearlite, additionally, spheroidizing of cementite and polygonization of the ferritic component are observed. A dependence of the character of fracture on the type of structure formed upon fatigue loading has been established. In the steel with a nonequilibrium structure of unannealed fine pearlite, an enhanced elasticity modulus, as compared to other more stable structures (coarse-lamellar, annealed fine, and spheroidized pearlite), and a reduction in the magnitude of the elasticity modulus under the action of cyclic loading have been found. It has been established that the structural changes in fine pearlite of laboratory specimens of the steel U10 upon cyclic tension are qualitatively similar to those in a railroad wheel of the steel 65G under the service conditions.
Keywords: high-carbon steels; pearlitic structures; cyclic tension; high-cycle fatigue; railroad wheel