Volume 119, Nº 9 (2018)

Spin-valve nanostructures with an exchange-coupled Gd/CoFe pair (synthetic ferrimagnet) as the free layer were prepared by magnetron sputtering. It was shown that when a fixed magnetic field is applied and the temperature near the compensation temperature of the synthetic ferrimagnet is varied, the spin valve switches between magnetic states, which are characterized by maximum and minimum resistance. The dependence of the compensation temperature on the Gd layer thickness is studied, which is interpreted based on the results of investigations of the microstructure of the Gd layer, taking into account peculiarities of its magnetic structure.

The present study examines the effect of various inhibitors on the structure and magnetic properties of nanocrystalline Fe_73.5Cu₁M₃Si_13.5B₉ alloys, where M = Nb, W, Mo, V, Cr, or a combination of these elements. The introduction of inhibitors with higher solubilities in α-Fe results in an increase in the lattice parameter of the Fe₃Si phase and induces a more marked drop in the initial permeability of the nanocrystalline alloy. A combination of several inhibitor elements is used and this allows an increase in the crystallization temperature and optimization of the core thermal treatment regime.

This paper presents the results of the study of the long-term relaxation states of metallic palladium-based foil filters (Pd, 9.6 at %; Y and Pd, 5.3 at %; In, 0.5 at %; Ru) after hydrogenation (82 000 and 58 500 h, respectively) using X-ray diffraction and synchrotron radiation (SR). We analyzed the normalized integral intensities of diffraction maxima for two orders of reflections from coherent scattering regions (CSRs) along crystallographic directions [111] and [100].

This paper presents the results of our investigation into the effects of О⁺ and Ar⁺ ion implantation and alternating implantation of Ar⁺ and О⁺ ions on the composition of nanoscale surface layers of a 50Cu–50Ni alloy. Our study showed that at the selected parameters of О⁺ ion irradiation, the formation of nanoscale surface layers of the investigated alloy depends on the chemical affinity of oxygen atoms to the alloy components rather than on the processes of radiation nature accompanying the irradiation. This paper analyzes the possible segregation processes of the alloy components under conditions of О⁺ and Ar⁺ ion irradiation.

This paper presents the results of investigation of alloys Hf–45% Ti and Hf–70% Ti structures which were formed under different kinetic conditions of the β → α (bcc → hcp) polymorphic transformation occurence. We used methods of metallography and EBSD analysis during our investigation. We have shown that the Hf–Ti alloys in the cast state exhibit a mixed structure consisting of α-phase crystals of several morphological types: large plates, groups of small parallel plates, and fine crystallites of the shape close to polyhedral. The α-phase structure of the Hf–Ti alloys after quenching consists of martensite crystals grouped into packets. In each packet, there are several crystallographic orientations of 12 possible orientations corresponding to Burgers orientation relationships, and no regular alternation of different orientations of the α phase were revealed in the packet. Irrespective of the cooling rate of the Hf–Ti alloys upon the β → α polymorphic transformation, within the initial β-phase grain, the same set of orientations of the α phase occurs. In the studied Hf–Ti alloys, the misorientation of substructure elements within the α-phase crystal reaches ~5.0° for the as-cast state and ~2.2° after quenching.

Scanning electron microscopy shows that in pure niobium deformed by shear under pressure, a grain structure characterized by an axial texture of recrystallization is formed from the textureless deformed state during annealing. The sharpest texture is formed during annealing at 800°C. The fraction of the area occupied by recrystallized grains, in which planes (110) are parallel to the sample plane, reaches 90%; the fraction of high-angle boundaries (HABs) is 40%; and the average grain-boundary (misorientation) angle is 17°. The texture forms during selective growth of recrystallization centers. The formation of new recrystallization centers in addition to deformation-induced growing centers during 900°C annealing slightly increases the fraction of HABs, the average misorientation angle, and creates a blurred recrystallization texture.

The paper discusses the influence of retained austenite formed in a structure after the phase transition in the bainitic temperature range on the properties of structural low-alloy steels. It is shown that the bainite transformation proceeds through two stages. The first stage is characterized by the formation of completely carbide-free bainite containing up to 45% retained austenite, which is stable under deep cooling. The second stage develops with increasing holding time and is accompanied by the release of carbides and a reduction in the amount of retained austenite. The mechanical properties of steels are given in terms of the morphology and chemical composition of the phases forming in the course of isothermal transformation in the bainitic temperature range.

The high Nb containing TiAl alloy with a nominal composition of Ti–44Al–8Nb–0.2W–0.2B–0.1Y was fabricated by a Vacuum Arc Remelting furnace. The microstructure and mechanical properties of specimens located in different sites of the ingot were investigated. Owing to the influence of melting process and electrode fabricating method, the morphologies and phase containing of this near lamellar structure in the top, middle, and bottom parts of ingot were different. The subtle difference in microstructure strongly influenced the room and high-temperature tensile properties in turn. However, the dominant influence factor of the mechanical properties was the defects at the bottom of this large-size ingot, though the bottom had the finest grain size.

New techniques of combined processes of metal pressing are being developed, which are aimed at eliminating billet length constraints, and which include two and more techniques of conventional deformation and severe plastic deformation. The main feature of such combined processes is that they either reduce or completely eliminate the drawbacks of individual processes of metal pressing involved in the combined process. In this work, we analyze how the integrated treatment and conventional techniques of drawing and equal-channel angular pressing (ECAP) as individual processes influence the formation of the ultra-fine-grained structure of copper and its ability to reach a high-strength state as a consequence of each of the involved processes. Copper wire is used as an example to illustrate the features of structure constituent refinements and changes in mechanical properties when the combined pressing–drawing technique with an equal-channel stepped matrix and the conventional drawing technique are used. The results show an increase in refinement of the copper structure both on the surface and in central regions of the wire. This indicates uniformity of the structure over the cross section and, hence, stability of the properties of the obtained wire with an ultra-fine-grained structure.