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Vol 118, No 11 (2017)

Electrical and Magnetic Properties

Domain structure and magnetization curves of films with perpendicular anisotropy

Dubovik M.N., Filippov B.N.

Abstract

Based on a two-dimensional micromagnetic simulation, the dependence of the period of a stripe domain structure on the thickness of Co(0001) and Ni(111) films has been obtained, which agrees well with the experimental data. A comparison has been carried out of the calculated and experimental hysteresis loops for a 50-nm Co film and 200-nm Ni film.

Physics of Metals and Metallography. 2017;118(11):1031-1039
pages 1031-1039 views

NMR and Mössbauer study of peculiarities of the structure formation in Fe–Сo alloys

Serikov V.V., Kleinerman N.M., Golovnya O.A.

Abstract

Fe–Co alloys with an Fe content of 20–95 at % have been investigated using NMR and Mössbauer spectroscopy. A comparison of the hyperfine fields measured at 59Со and 57Fe nuclei on the same samples allowed us to determine that the magnetic moment at an Fe atom in the disordered alloys with Fe concentrations of 20–80 at % varies from 2.8 to 2.4 μB, as well as to ascertain peculiarities of the formation of an ordered state. The data obtained indicate the existence of regions with a short-range order of the D03 type in alloys with an Fe content of 70–80 at %. In alloys with iron concentrations greater that 80 at %, the phase separation of the structure into regions of elemental iron and short-range-ordered Fe89Co11 regions is observed. The obtained results explain the contradictions in the values of the magnetic moment at the Fe atom and the anomalous dependence of the lattice parameter of the alloy with a Со content less than 20 at %, as well as prove the accuracy of the phase diagram containing regions of three bcc phases, rather than one, as is commonly accepted.

Physics of Metals and Metallography. 2017;118(11):1040-1047
pages 1040-1047 views

Dynamics of a lattice of magnetic nanoparticles under action of a pulse of a magnetic field

Shutyi A.M., Sementsov D.I.

Abstract

Processes of quasistatic and dynamic magnetization reversal have been studied for the case of planar 6 × 6 lattices of magnetic nanodipoles that possess a cubic crystallographic anisotropy. The response of the total magnetic moment to a magnetic-field pulse of various duration and polarization have been determined for different equilibrium configurations of the lattices. Along with the in-plane configurations of magnetic moments, configurations with one and two dipoles oriented perpendicular to the plane of the lattices have been considered.

Physics of Metals and Metallography. 2017;118(11):1048-1058
pages 1048-1058 views

Structure, magnetic and magnetocaloric properties of nonstoichiometric TbCo2Nix compounds

Inishev A.A., Gerasimov E.G., Mushnikov N.V., Terent’ev P.B., Gaviko V.S.

Abstract

The structure and magnetic and magnetocaloric properties of new nonstoichiometric TbCo2Nix compounds (0 ≤ x ≤ 0.4) have been studied. The alloys with х ≤ 0.1 have been shown to be single-phase with the MgCu2-type structure; in alloys with х > 0.1, an additional phase with a PuNi3-type structure has been formed. It has been found that the concentration dependences of the Curie temperature and magnetic moment of the 3d-metal sublattice have a maximum at x = 0.025. The magnetocaloric effect magnitude for the TbCo2Nix compounds has been estimated using the results of magnetic and heat-capacity measurements.

Physics of Metals and Metallography. 2017;118(11):1059-1065
pages 1059-1065 views

Structure, Phase Transformations, and Diffusion

Microstructure and properties of surface-modified tungsten powders mechanically activated in different media

Savenko V.I., Toporov Y.P., Chernyshev V.V., Malkin A.I.

Abstract

The results of an experimental-theoretical study of the effect of thin-film coatings on residual microstrains, microstresses, and local microdistortions of the atomic structure of powder tungsten mechanically activated in the centrifugal ball mill have been presented. It has been shown that microdistortions of the crystal structure of different system-hierarchical levels arise in the surface-oxidized powders, which increase with an increase in the time of the activation process. It has been shown that this should lead to a significant increase in the reactivity of the mechanically activated powder tungsten. In contrast, the adsorption films that plasticize the near-surface layer of particles can decrease the efficiency of the mechanoactivation process of the tungsten powder.

Physics of Metals and Metallography. 2017;118(11):1066-1072
pages 1066-1072 views

Structure of nickel–copper alloys subjected to high-pressure torsion to saturation stage

Popov V.V., Stolbovsky A.V., Popova E.N.

Abstract

Transmission electron microscopy and microhardness measurements were used to study the structure of Ni–Cu alloys subjected to high-pressure torsion (to saturation state) at room-temperature using five revolutions. It was shown that, when passing from copper to nickel, the submicrocrystalline structure becomes substantially refined, and the microhardness increases by more than 1.5 times. This is related to differences in the melting temperature and stacking fault energy. The simultaneous effect of these two factors leads to the nonlinearity of the composition dependences of the crystallite size and microhardness.

Physics of Metals and Metallography. 2017;118(11):1073-1080
pages 1073-1080 views

Features of austenite formation in low-carbon steel upon heating in the intercritical temperature range

Panov D.O., Smirnov A.I.

Abstract

The features of austenite formation upon continuous heating of low-carbon steel at the rates of 90–0.15 K/s in the intercritical temperature range (ICTR) have been studied. It has been found that, in the initially high-tempered, initially quenched, and initially cold-deformed steel, the α → γ transition in the ICTR consists of three stages. The thermokinetic diagrams of the austenite formation with the indication of the positions of the critical points Ac1 and Ac3 and also of the temperature ranges of the development of each identified stage of the α → γ transformation have been constructed. A complex of structural studies has been carried out, and a scheme of the austenite formation upon continuous heating at a rate of 90 K/s in the ICTR for the initially high-tempered steel, initially quenched steel, and initially cold-deformed low-carbon steel has been suggested, which reflects all stages of this process.

Physics of Metals and Metallography. 2017;118(11):1081-1090
pages 1081-1090 views

Grain-boundary diffusion of cobalt in submicrocrystalline molybdenum obtained by high-pressure torsion

Popov V.V., Sergeev A.V.

Abstract

Radiometric layer-by-layer analysis has been used to study the grain-boundary diffusion of Co in submicrocrystalline Mo produced by severe plastic deformation using high-pressure torsion. It has been found that, under severe plastic deformation, nonequilibrium grain boundaries have been formed, which are ultrafast diffusion paths. During annealing, the recovery of nonequilibrium grain boundaries takes place. The properties of boundaries that underwent the recovery were shown to be close to those of boundaries originated by recrystallization in coarse-grained Mo. As the annealing temperature increases, the fraction of nonequilibrium boundaries decreases; and beginning from 823 K, there are no more nonequilibrium boundaries in the structure.

Physics of Metals and Metallography. 2017;118(11):1091-1096
pages 1091-1096 views

Investigation of the effect of aluminum on the phase composition of Ti–Al–Nb–Mo gamma alloys

Terlikbaeva A.Z., Alimzhanova A.M., Shayakhmetova R.A., Smagulov D.U., Osipov P.A.

Abstract

A quantitative analysis of the influence of aluminum concentration on the phase composition of TNM-type Ti–Al–Nb–Mo γ-alloys has been carried out using the Thermo-Calc software and experimental methods. Isothermal and polythermal sections of the corresponding phase diagram have been calculated; the critical temperatures of phase transformations in the alloys of the system, and the chemical compositions of phases formed in them (β, α, α2, γ) have been determined. The influence of the annealing temperature on the microstructure and phase composition of the alloys containing 43 and 40% Al has been studied.

Physics of Metals and Metallography. 2017;118(11):1097-1104
pages 1097-1104 views

Effect of ultrasonic casting on microstructure and its genetic effects on corrosion performance of 7085 aluminum alloy

Liu Y., Huang Y., Xiao Z.

Abstract

The effect of ultrasonic casting on microstructure and its genetic effects on strength, exfoliating corrosion, stress corrosion and electrochemical behavior of 7085 aluminum alloy have been investigated by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM), together with tensile testing, exfoliation corrosion testing, electrical conductivity testing and polarization curve. The results indicate that ultrasonic casting could refine the grain, alleviate segregation and inhibit the formation of coarse nonequilibrium phase in as-cast state; in addition, the dissolution of nonequilibrium phase in the ultrasonic ingot during homogenization turns out to be more thorough. What is more, the plate processed from ultrasonic ingot holds a lower ratio of recrystallization after solid solution, and the corrosion performance of the alloy was improved under T6 temper, without sacrifice of strength, owing to the dispersive distribution of strengthening phase in the matrix and the coarse, sparse GBPs.

Physics of Metals and Metallography. 2017;118(11):1105-1112
pages 1105-1112 views

Effect of friction-induced deformation and oxidation on the structure and microhardness of surface aluminum and silumin layers

Korshunov L.G., Chernenko N.L., Brodova I.G., Shirinkina I.G.

Abstract

Metallography, electron microscopy, and X-ray diffraction have been used to investigate structural transformations that take place in a 10-μm-thick surface layer in aluminum and Al–17% Si alloy under conditions of sliding friction and subsequent oxidation at 100 and 200°C for 1 h. Friction-induced deformation has been carried out at room temperature in air and at–196°C in liquid nitrogen by reciprocating sliding of a cylindrical indenter made of cubic boron nitride at a rate of 0.014 m/s and a load of 98 N. It is shown that deformation under these conditions forms nanocrystalline structures in the surface layer in aluminum and Al–17% Si alloy and increases their microhardness by a factor of 1.8–3.5. A high contact deformation and a high affinity of oxygen to aluminum and silicon cause the formation of anomalously supersaturated solid solutions of oxygen in aluminum and silicon in the surface layer of the alloy during friction. Oxidation at 100°C (1 h) of the deformed Al–17% Si alloy increases its microhardness due to the decomposition of anomalously supersaturated solid solutions of oxygen in aluminum and silicon and the formation of their oxides.

Physics of Metals and Metallography. 2017;118(11):1113-1119
pages 1113-1119 views

Diffusion formation of intermediate phases and supersaturated solid solutions in the aluminum−copper system

Goreslavets N.N., Rodin A.O.

Abstract

Studies of the processes that occur upon the interdiffusion in the aluminum−copper system in the temperature range of 320–440°C have been carried out using optical metallography, scanning electron microscopy, and electron microprobe analysis. It has been found that, in this system, at low annealing temperatures, there are no intermediate phases that correspond to the equilibrium phase diagram. Short-term high-temperature annealing leads to the formation of the equilibrium phases. The subsequent low-temperature annealing leads to the precipitation of a second phase from the solid solution in the form of particles rather than layers. It has been shown that the absence of the equilibrium phases is accompanied by the formation of a supersaturated solid solution of copper in aluminum.

Physics of Metals and Metallography. 2017;118(11):1120-1126
pages 1120-1126 views

Temperature dependence of copper diffusion in different thickness amorphous tungsten/tungsten nitride layer

Asgary S., Hantehzadeh M.R., Ghoranneviss M.

Abstract

The amorphous W/WN films with various thickness (10, 30 and 40 nm) and excellent thermal stability were successfully prepared on SiO2/Si substrate with evaporation and reactive evaporation method. The W/WN bilayer has technological importance because of its low resistivity, high melting point, and good diffusion barrier properties between Cu and Si. The thermal stability was evaluated by X-ray diffractometer (XRD) and Scanning Electron Microscope (SEM). In annealing process, the amorphous W/WN barrier crystallized and this phenomenon is supposed to be the start of Cu atoms diffusion through W/WN barrier into Si. With occurrence of the high-resistive Cu3Si phase, the W/WN loses its function as a diffusion barrier. The primary mode of Cu diffusion is the diffusion through grain boundaries that form during heat treatments. The amorphous structure with optimum thickness is the key factor to achieve a superior diffusion barrier characteristic. The results show that the failure temperature increased by increasing the W/WN film thickness from 10 to 30 nm but it did not change by increasing the W/WN film thickness from 30 to 40 nm. It is found that the 10 and 40 nm W/WN films are good diffusion barriers at least up to 800°C while the 30 nm W/WN film shows superior properties as a diffusion barrier, but loses its function as a diffusion barrier at about 900°C (that is 100°C higher than for 10 and 40 nm W/WN films).

Physics of Metals and Metallography. 2017;118(11):1127-1135
pages 1127-1135 views

Strength and Plasticity

A comparative study of microstructure, oxidation resistance, mechanical, and tribological properties of coatings in Mo–B–(N), Cr–B–(N) and Ti–B–(N) systems

Kiryukhantsev-Korneev F.V., Novikov A.V., Sagalova T.B., Petrzhik M.I., Levashov E.A., Shtansky D.V.

Abstract

M–B–(N) (M = Mo, Cr, Ti) coatings were obtained by the magnetron sputtering of MoB, CrB2, TiB, and TiB2 targets in argon and in gaseous mixtures of argon with nitrogen. The structure and composition of the coatings have been investigated using scanning electron microscopy, glow-discharge optical emission spectroscopy, and X-ray diffraction. The mechanical and tribological properties of the coatings have been determined by nanoindentation, scratch-testing, and ball-on-disk tribological tests. The experiments on estimating the oxidation resistance of coatings were carried out in a temperature range of 600–1000°С. A distinctive feature of TiB2 coatings was their high hardness (61 GPa). The Cr–B–(N) coatings had high maximum oxidation resistance (900°С (CrB2) and 1000°С (Cr–B–N)) and possessed high resistance to the diffusion of elements from the metallic substrate up to a temperature of 1000°С. The Mo–B–N coatings were significantly inferior to the Ti–B–(N) and Cr–B–(N) coatings in their mechanical properties and oxidation resistance, as well as had а tendency to oxidize in air atmosphere after long exposure at room temperature. All of the coatings with nitrogen possessed a low coefficient of friction (in a range of 0.3–0.5) and low relative wear ((0.8–1.2) × 10–6 mm3 N–1 m–1.

Physics of Metals and Metallography. 2017;118(11):1136-1146
pages 1136-1146 views

Anticorrosion properties of textured substrates made of copper–nickel-based ternary alloys

Khlebnikova Y.V., Suaridze T.R., Rodionov D.P., Egorova L.Y., Gervas’eva I.V., Gulyaeva R.I.

Abstract

The tendency of some copper–nickel-based ternary alloys with additions of 3d transition metals, such as Cr, V, and Fe, to oxidation has been studied. The resistance to the oxidation was evaluated by the thermogravimetry method. It has been established that the strengthened textured tapes made of the Cu–40% Ni–1.2% Cr and Cu–40% Ni–1.4% Fe alloys have significantly better anticorrosive properties at 700°C than tapes made of pure copper and other investigated alloys, and can be used as substrates for epitaxial deposition of buffer and superconducting layers at elevated temperatures.

Physics of Metals and Metallography. 2017;118(11):1147-1154
pages 1147-1154 views

Structure, properties, and resistance to stress-corrosion cracking of a nitrogen-containing austenitic steel strengthened by thermomechanical treatment

Mushnikova S.Y., Kostin S.K., Sagaradze V.V., Kataeva N.V.

Abstract

The results of comparative studies of the structure, mechanical properties, and resistance to stresscorrosion cracking (SCC) in the chloride solutions of a Cr–Mn–Ni austenitic nitrogen-containing steel (20Cr–6Ni–11Mn–1.5Mo–N–V–Nb) produced with the use of different regimes of the high-temperature thermomechanical treatment (HTTMT) have been presented. An unfavorable effect of the grain-boundary precipitates of the nitride phase on the impact toughness and resistance to SCC has been found. It has been shown that the strengthening of nitrogen-containing steel upon HTTMT, which ensures an increase in the yield stress by 1.8 times compared to the austenitized state, does not decrease the resistance to SCC.

Physics of Metals and Metallography. 2017;118(11):1155-1166
pages 1155-1166 views

Evolution of microstructure and mechanical properties of steel in the course of pressing–drawing

Lezhnev S.N., Volokitina I.E., Volokitin A.V.

Abstract

The combined continuous pressing–drawing process is proposed after a comprehensive analysis of available plastic structure-forming techniques taking into account the promising trends in their development. This combination of severe plastic deformation in equal-channel step die and drawing allows one to obtain a wire of desired size and shape in the cross section with an ultrafine-grained structure after a few deformation cycles. It also enables initial workpieces of any length to be processed and, therefore, allows one to obtain finished products up to several tens of meters in length. The aim of this study is to investigate the effect of new combined pressing–drawing technique of plastic deformation on the structure and mechanical properties of the steel. These studies have shown that the proposed deformation technique has a significant advantage of the techniques currently used to manufacture a steel wire.

Physics of Metals and Metallography. 2017;118(11):1167-1170
pages 1167-1170 views