Physics of Metals and Metallography (v.113, #5)

The aim of this investigation is to establish the effect of relaxation on the formation of ordered substitutional solid solutions in Al1 − x M x alloys (M = 3d metal; x = 1.6 at %). As the main parameters of the process of formation of the aluminum-based solution, thermodynamic quantities such as the energy of dissolution and the cohesive energy have been chosen; for choosing the most appropriate substitutional element, an analysis of the relaxation energy and deviations of empirical atomic radii of the impurity from the radius of the matrix-forming element has been suggested. It has been shown that there is a correlation between these thermodynamic quantities through the behavior of the density of electronic states and the Fermi energy. A regular relation has also been demonstrated to exist between the relaxation and stability of arising solid solutions, which supports the applicability of the analysis of relaxation energy depending on the atomic radius of the matrix-substituting element. The presence of anomalies in the behavior of magnetic properties of some aluminum alloys with transition metals has been shown and their explanation is given.
Keywords: relaxation; aluminum; transition metals; density of electronic states; dissolution energy; cohesive energy; alloy formation

Symmetry of pretransition structures in alloys with a B2-type superstructure by Yu. S. Zolotukin; A. I. Lotkov; A. A. Klopotov; V. N. Grishkov (438-447).
Transformation properties of the order parameters—atomic displacements in the B2 structure related to the wave vectors of the 1/3〈110〉 and 1/3〈111〉 type, which, in particular, are observed in B2 titanium nickelide-based alloys, have been studied. Irreducible representations and their basis vectors related to these wave vectors have been determined. Subgroups of the symmetry group O h 1 of the B2 structure relative to which the order parameters are invariant have been calculated. The feasibility of the realization of these subgroups as symmetry groups of the pretransition structures that arise prior to the B2 → R martensitic transformation in titanium nickelide-based alloys has been analyzed.
Keywords: pretransition structures; martensitic transformations; irreducible representations; space groups; wave vectors; basis vectors of irreducible representations; B2 structure

A Fourier-transform-based method for the calculation of stresses produced by dislocations in multilayer materials is proposed. In order to illustrate the approach proposed, the components of the stress tensor of a screw dislocation in a solid with a coating have been calculated and the equilibrium position of the dislocation near the interface has been determined. It is demonstrated that the ratio α = a/l of the equilibrium position a of the dislocation to the coating thickness l is asymptotically proportional to the ratio q = μ12 of the shear moduli of the coating and the substrate material.
Keywords: dislocation; multilayer material; stress function; Poisson equation; Fourier transform; asymptotic solution

Effect of neutron irradiation on the properties of the FeSe compound in the superconducting and normal states by A. E. Kar’kin; T. Wolf; A. N. Vasil’ev; O. S. Volkova; B. N. Goshchitskii (455-459).
The influence of atomic disorder induced by irradiation with fast neutrons on the properties of normal and superconducting states of polycrystalline samples of FeSe has been studied. The irradiation with fluences of fast neutrons up to 1.25 × 1020 cm−2 at the irradiation temperature T irr ≈ 50°C leads to relatively small changes in the temperature T c of the superconducting transition and in the electrical resistivity ρ25 at 25 K. This behavior is related to the relatively low concentration of radiation defects arising at a given irradiation temperature, which is a consequence of a specific crystal structure of FeSe, which is more simple as compared to other layered compounds of this class.
Keywords: superconductivity; FeSe; irradiation by fast neutrons; transport properties

Magnetic state and magnetocaloric properties of rapidly quenched Gd75 M 25 alloys (M = Co, Ni) by D. A. Shishkin; A. S. Volegov; S. V. Andreev; N. V. Baranov (460-465).
Effect of rapid quenching on the magnetic state and magnetocaloric properties of the Gd3Co and Gd3Ni intermetallic compounds has been studied. The rapidly quenched Gd75Co25 and Gd75Ni25 alloys were found to exhibit a ferromagnetic behavior below the Curie temperature T C = 172 and 117 K, respectively, whereas their crystalline counterparts Gd3Co and Gd3Ni are characterized by an antiferromagnetic order and Néel temperatures T N = 130 and 99 K, respectively. Data have been obtained which indicate that the amorphization of Gd3Co leads to the appearance of a magnetic moment at cobalt atoms. The rapid quenching is shown to lead to a significant increase in the low-field magnetocaloric effect.
Keywords: magnetocaloric effect; gadolinium; rare-earth intermetallic compounds; amorphous alloys

Calorimetric effects during the α → γ transformation in Fe-Ni-Ti metastable alloys by N. D. Zemtsova; M. A. Eremina; V. A. Zavalishin (466-479).
A calorimetric study of the reverse α → γ transformation has been carried out in five metastable Fe-Ni-Ti alloys. The amount of the α phase in the initial samples is more than 50%. The exothermic processes of the decomposition of the α and γ phases exceed the endothermic reactions of formation of the reverted austenite upon heating to the midpoint of the temperature interval of the reverse α → γ transformation. In the middle part of the interval in which the maximum rate of the transformation is recorded by the magnetometric method, the calorimetric curve does not exhibit thermal effects. This disagreement indicates the complex character of the transformation. At the finishing stage of the α → γ transformation, there is clearly detected an endothermic reaction.
Keywords: Fe-Ni-Ti; mechanism of the reverse α → γ transformation; differential scanning calorimetry (DSC); magnetometry

Microstructure and properties of low-carbon weld steel after thermomechanical strengthening by V. M. Schastlivtsev; T. I. Tabatchikova; I. L. Yakovleva; S. Yu. Klyueva; A. A. Kruglova; E. I. Khlusova; V. V. Orlov (480-488).
Optical metallography and transmission electron microscopy have been used to study the structure of the rolled sheets produced from the pipe steel of Kh90 class. The sheets were manufactured using different technological schemes of strengthening: direct quenching from rolling heating (QRH) followed by high-temperature tempering; and two-step thermomechanical treatment with rapid cooling to a desired temperature (TMT). A relationship between the nature of the structure and mechanical properties of the rolled sheet has been established. It has been shown that the two-step thermomechanical treatment has significant advantages over the quenching from the rolling heating, which is related to the formation of highly dispersed bainite with a subgrain structure upon TMT.
Keywords: low-carbon steel; thermomechanical treatment; quenching from rolling heating; structure; mechanical properties

Deformation-induced cyclic phase transitions of dissolution-precipitation of nitrides in surface layers of Fe-Cr-(Ni)-N alloys by V. A. Shabashov; S. V. Borisov; A. V. Litvinov; V. V. Sagaradze; A. E. Zamatovskii; K. A. Lyashkov; N. F. Vil’danova (489-503).
Methods of Mössbauer spectroscopy, transmission electron microscopy, and X-ray diffraction have been used to study structural and phase transformations in surface layers of iron and Fe-Cr-(Ni) alloys subjected to ion-plasma nitriding and subsequent severe cold plastic deformation by shear under pressure in Bridgman anvils. It has been shown that the cyclic phase transformations of dissolution-precipitation of nitrides in the alloys result in the formation of nitrogen-supersaturated solid solutions, precipitation of secondary nitrides, and the nanostructurization of the metallic matrix. It has been established that the introduction of chromium into iron alloys accelerates the formation of nitrides upon nitriding and makes it possible to obtain solid solutions strongly supersaturated with nitrogen (more than 10 at % N in the fcc lattice) during subsequent deformation.
Keywords: Fe-Cr-(Ni)-N; ion-plasma nitriding; mechanical alloying; nanostructurization; surface; Mössbauer spectroscopy

NiCrM (M = W, Mo, V) ternary alloy tapes as cube-textured substrates for second-generation superconducting cables by D. P. Rodionov; I. V. Gervas’eva; Yu. V. Khlebnikova; V. A. Kazantsev; V. A. Sazonova (504-512).
Development of the deformation texture and recrystallization processes have been studied in some ternary nickel-based alloys of the Ni-Cr-W, Ni-Cr-Mo, and Ni-Cr-V systems. An optimum relationship between the amounts of the alloying elements upon the combined alloying of nickel has been found. Problems of the optimization of the regimes of recrystallization annealing have been considered, which are related to an increase in the temperature of the onset of primary recrystallization in ternary nickel alloys after deformation by rolling to large reductions. An analysis of mechanical and magnetic properties of all the alloys has been performed.
Keywords: ternary nickel alloys; combined alloying; cold deformation by rolling; recrystallization annealing; perfect cube texture

Oxygen isotope exchange in nanosized powders of the Al2O3 oxide by A. V. Bagazeev; V. B. Vykhodets; E. V. Vykhodets; T. E. Kurennykh; A. Ya. Fishman; T. M. Demina; A. I. Medvedev; A. M. Murzakaev (513-519).
Oxygen isotope exchange (OIE) between nanosized powders of the aluminum oxide Al2O3 and oxygen-containing gases 18O2 and C18O2 has been studied in a temperature range of 100–500°C. The concentration of the oxygen isotope 18O in the powders was determined by nuclear microanalysis technique (NRA). It has been shown that for this oxide the OIE exhibits a significant size effect. It has been established that the OIE of the Al2O3 nanopowder is characterized by a specific time dependence of the concentration of the 18O isotope at the surface of grains and by a low level of the content of 18O in the oxide. A linear dependence of the concentration of 18O in the nanopowders on the specific surface of the nanoparticles has been revealed. The experimental data are discussed in terms of several models of the process of isotope exchange.
Keywords: aluminum oxide; nanopowder; oxygen isotope exchange; nuclear microanalysis; tracers

At present, it is the austenitic cold-deformed steel EK164 (06Kh16N20M2G2BTFR)-ID that is considered as a promising material for the achievement of a maximum damage (no less than 110 dpa) and maximum burnup (≥15%). In this work, we have determined the characteristics of porosity formed upon irradiation in a BN-600 reactor to the maximum damaging dose of 77 dpa in the materials of fuel-element cans made of cold-deformed steel EK164-ID c.d. A comparison has been made with analogous characteristics obtained earlier using the standard material, i.e., the cold-deformed steel ChS68 (06Kh16N 15M2G2TFR)-ID c.d.
Keywords: austenitic steel; neutron irradiation; reactor BN-600; rate of dose accumulation; swelling; characteristics of porosity