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The phase composition and heat conductivity of (ZrO2)0.9(R2O3)0.1 solid solution single crystals have been studied, where R = (Gd, Yb, Sc, Y), (ZrO2)0.9(Sc2O3)0.09(Gd2O3)0.01 and (ZrO2)0.9(Sc2O3)0.09(Yb2O3)0.01. Single crystals have been grown by directional melt crystallization in a cold skull. The phase composition of the crystals has been studied using X-ray diffraction and Raman spectroscopy. The heat conductivity of the crystals has been studied using the absolute steady-state technique of longitudinal heat flow in the 50—300 K range. We show that at a total stabilizing oxide concentration of 10 mol.% the phase composition of the crystals depends on the ionic radius of the stabilizing cation. The (ZrO2)0.9(Sc2O3)0.1 crystals have the lowest heat conductivity in the 50—300 K range while the (ZrO2)0.9(Gd2O3)0.1 solid solutions have the lowest heat conductivity at 300 K.Analysis of the experimental data suggests that the heat conductivity of the crystals depends mainly on the phase composition and ionic radius of the stabilizing cation. Phonon scattering caused by the difference in the weight of the co-doping oxide cation has a smaller effect on the heat conductivity.

A diffusion welding of coarse-grained and ultrafine-grained (UFG) specimens of titanium near-α alloy Ti-5Al-2V used in nuclear power engineering was made by Spark Plasma Sintering. The failure of the welded specimens in the conditions of hot salt corrosion and of electrochemical corrosion were shown to have preferentially intercrystalline character. In the case of presence of macrodefects, crevice corrosion of the welded joints was observed. The resistance of the alloys against the intercrystalline corrosion was found to be determined by the concentration of vanadium at the titanium grain boundaries, by the size and volume fraction of the β-phase particles and by the presence of micro- and macropores in the welded joints. The specimens of the welded joints of the UFG alloy have higher hardness, hot salt corrosion resistance and the electrochemical corrosion.

The conductor aluminum alloys Al-0.25wt.%Zr doped additionally with Х = Er, Si, Hf, and Nb were the objects of investigations. The fine-grained microstructure in the alloys was formed by Equal Channel Angular Pressing and Rotary Swaging. The thermal stability of the microstructure, specific electrical resistivity, and microhardness of the novel conductor aluminum alloys was investigated. The mechanisms of nucleation of the Al3(Zr,X) secondary particles during annealing the fine-grained aluminum alloys were determined using Jones-Mehl-Avrami-Kolmogorov equation. Using Zener equation, the dependencies of the mean secondary particle sizes on the annealing time were obtained on the base of analysis of the data on the grain growth in the aluminum alloys. The secondary particle nucleation during long-time low-temperature annealing (300 оC, 1000 hrs) was shown to go preferentially at the cores of the lattice dislocations. The Al-0.25%Zr-0.25%Er-0.20%Hf-0.15%Si alloy subjected to long-time annealing at 300 оC has the optimal combination of the microhardness and electrical conductivity (59.8%IACS, Hv = 480 ± 15 MPa).

Behavior of Pt/C catalysts obtained by the platinum deposition on standard and nitrogen-doped carbon supports with different microstructure has been studied in the oxygen electroreduction reaction in an acidic electrolyte. The catalysts based on the modified supports are characterized by a uniform spatial distribution of small-sized (1.5–2 nm) Pt nanoparticles over the surface of the supports, which results in high values of the electrochemically active surface area (110–130 m2 g− 1 (Pt)). The use of various stress testing protocols has shown that the Pt/C material based on the N-doped KetjenBlack EC DJ-600 possesses the highest mass activity and durability, which noticeably exceed the corresponding characteristics of the commercial HiSPEC3000 catalyst.

Metallic zirconium based glasses are a new promising family of materials characterized by high strength and comparatively high plasticity in compression tests. In recent years, great attention has been paid to the application of different regimes for the treatment of metallic glasses for the formation of a unhomogeneous amorphous structure to increase the plasticity of these materials. In this study, amorphous Zr62.5Cu22.5Fe5Al10 alloy bands were manufactured by the method of quenching on a rotary copper disk. The effect of hot rolling and further annealing at a temperature of 300°C for 150 min on the structure and properties of these bands was investigated. To study the transformation occurring in their structure as a result of thermomechanical treatment, transmission electron microscopy and X-ray diffraction were used. The effect of thermomechanical treatment on the mechanical properties of bands was studied by measuring the Vickers microhardness. Based on the obtained results, some conclusions about the effect produced by the microstructure of bands on the microhardness of the Zr62.5Cu22.5Fe5Al10 alloy were made. In this study, an abrupt increase in the microhardness was observed after thermomechanical treatment, due to the formation of nanosized uniformly distributed areas in the structure.

t—The diffusion welding of ultrafine-grained pseudo-α-titanium Ti–4.73% Al–1.88% V alloy specimens has been performed by spark plasma sintering. It has been shown that the destruction of welded joints in the ultrafine-grained (UFG) specimens under hot salt corrosion (HSC) conditions has a two-stage character: intercrystallite corrosion (ICC) is developed at the first stage to turn into pitting corrosion at the following stage. It has been established that the resistance to intercrystallite corrosion is governed by the concentration of vanadium on grain boundaries, the size and volumetric content of β-phase particles, and the existence of pores in a welded joint. It has been demonstrated that the welded joints of the ultrafine-grained specimens have higher hardness and resistance to intercrystallite corrosion as compared to coarse-grained specimens.

(ZrO2)1-x(Gd2O3)x (x= 0.028–0.04) is heat-treated at 1600°C in air or in vacuum. Partially gadolinia-stabilized zirconia crystals are grown by the skull melting technique. The effect of annealing on the phase compositions, structures, and mechanical properties of the crystals is studied using X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and indentation. A comparison with previously obtained data on the structure and properties of crystals after growth shows that annealing the crystals leads to the redistribution of gadolinia between the tetragonal phases: the t phase is depleted of gadolinia while the t’ phase becomes enriched. The gadolinia-enriched t’ phase undergoes multistage twinning. Thus, the sizes of the twins in the t’ phase are far smaller than those in the t phase. Annealing the crystals increases their fracture toughness, and this increase is larger for all crystals after air annealing. The increase in the fracture toughness of the crystals is caused by a decrease in the gadolinia concentration in the transformable t phase, which enhances the effect of the transformation hardening mechanism. The fracture toughness of the crystals is further increased by the ferroelastic hardening mechanism, the effect of which is enhanced with an increase in the quantity of the t’ phase in the crystals.

Due to their tunable current–voltage characteristics, Zn-doped thin SiO2 films are promising for microelectronic devices, e.g., memristors. In this work we studied single-crystal Si (100) substrates with 200 nm SiO2 surface layers implanted with 64Zn+ using Zn K-edge x-ray absorption spectroscopy (XAS), transmission electron microscopy (TEM) and electron diffraction. We used two specimens: as-implanted and annealed in oxygen at 700°C. Cross-section TEM analysis showed that 64Zn+ implantation leads to the formation of a subsurface layer consisting of Zn nanoparticles approximately 7 nm in size. The nanoparticles are distributed in depths from 10 nm to 90 nm, with a concentration peak at 45 nm. Electron microscopy showed that most of the Zn nanoparticles are amorphous. However, XAS data indicated that almost all the Zn atoms are coordinated with oxygen. Thus, only a small fraction of zinc atoms are involved in the formation of nanoclusters. Annealing at 700°C leads to the oxidation of particles with the formation of the Zn2SiO4 phase. The particle sizes in the surface layer of SiO2 after annealing vary from 3 nm to 20 nm.

In this work we explored the possibility of obtaining single-phase β-Zn4Sb3 material by direct melting and spark plasma sintering (SPS). The effect of the SPS conditions and synthesized material composition on the structure and thermoelectric properties of the material was studied. X-ray diffraction was used for phase analysis, and scanning electron microscopy was used for characterizing the morphology of the bulk samples. We found electro-migration of Zn due to the exposure to DC pulses during SPS at 40 MPa. Zinc electro-migration produced a zinc-excess layer on the sample surface on the cathode side and a zinc-depleted layer, i.e., ZnSb, on the anode side of the sample. We show that an increase in the sintering pressure, and hence a decrease in the electric current passing through the material, produces single-phase β-Zn4Sb3 material in the entire sample bulk, provided the synthesized material contains excess zinc. The highest ZT of ∼ 1.28 at 673 K was obtained for the material synthesized with Zn excess and sintered by SPS at a pressure of 100 MPa.

Cerium is a promising alloying element that may improve the mechanical properties of aluminum-based alloys. However, the effect of Ce on the microstructural and mechanical behavior of complex-alloyed aluminum-based alloys has not been studied well. In this work, we have analyzed the effect of Ce and Fe co-addition on the phase structure, grain structure, and tensile characteristics of the Al-Mg alloy at ambient and elevated temperatures. X-ray and microstructural studies involving scanning electron and transmission electron microscopy methods have been used in order to identify the phase composition of the Al-Mg-Fe-Ce alloy. Two Ce-bearing constituent phases have been identified and their morphology has been analyzed. Uniaxial tensile test experiments were used to study the mechanical characteristics of the samples processed by simple thermomechanical treatment. The Ce- and Fe-modified alloy exhibits fine-grained structure and superplasticity at sub-solidus temperatures, increased yield strength, and good room temperature ductility.

The effect of temperature modes and heating rates (Vh) on the shrinkage kinetics of submicron and fine aluminum oxide powders has been studied. The objects of research comprised (i) submicron alfa-Al2O3 powder, (ii) submicron alfa-Al2O3 powder with an amorphous layer on particle surface, (iii) fine alfa-Al2O3 powder. The alumina ceramic specimens were produced by Spark Plasma Sintering (SPS). Equally fine powders (i) and (ii) were used to analyze the effect of an amorphous layer on sintering kinetics. Powders (i) and (iii) were used to analyze the effect of the initial particle size on shrinkage kinetics. Shrinkage curves were analyzed using the Young-Cutler and Coble models. It has been shown that sintering kinetics is determined by the intensity of grain boundary diffusion for submicron powders and by simultaneous lattice and grain boundary diffusion for fine powders. It has been determined that an amorphous layer on the surface of submicron alfa-Al2O3 powder affects grain boundary migration rate and the Coble equation parameters at SPS final stages. It has been suggested that abnormal characteristics of the alumina ceramics sintered from a submicron powder with an amorphous layer on the particle surface are associated with an increased concentration of defects at grain boundaries that were formed during crystallization of the amorphous layer., Comment: 62 pages, 20 figures, 5 tables, 67 references

The results of investigation of crystal structure, ion conductivity and local structure of solid solutions (ZrO2)1−x(Gd2O3)x and (ZrO2)1−x(Y2O3)x (x = 0.04, 0.08, 0.10, 0.12, 0.14). The crystals were grown by directional crystallization of the melt in a cold container. The phase composition of the crystals was studied by X−ray diffractometry and transmission electron microscopy. Transport characteristics were studied by impedance spectroscopy in the temperature range 400—900 °C. The local crystal structure was studied by optical spectroscopy. Eu3+ ions were used as a spectroscopic probe. The results of the study of the local structure of solid solutions of ZrO2—Y2O3 and ZrO2—Gd2O3 systems revealed the peculiarities of the formation of optical centers, which reflect the nature of the localization of oxygen vacancies in the crystal lattice depending on the stabilizing oxide concentration. It is established that the local crystal environment of Eu3+ Ions in solid solutions (ZrO2)1−x(Y2O3)x and (ZrO2)1−x(Gd2O3)x is determined by the stabilizing oxide concentration and practically does not depend on the type of stabilizing oxide (Y2O3 or Gd2O3). The maximum conductivity at 900 °C was observed in crystals containing 10 mol.% Gd2O3 and 8 mol.% Y2O3. These compositions correspond to the t′′−phase and are close to the boundary between the regions of the cubic and tetragonal phases. It was found that in the system ZrO2—Y2O3 stabilization of the highly symmetric phase occurs at a lower stabilizing oxide concentration than in the system ZrO2—Gd2O3. Analysis of the data obtained allows us to conclude that in this range of compositions the main influence on the concentration dependence of the ion conductivity has a phase composition, rather than the nature of the localization of oxygen vacancies in the crystal lattice.

Crystals of (ZrO2)1 –x – y(Sc2O3)x(Y2O3)y (x = 0.003–0.045, y = 0.005–0.03) solid solutions have been grown by directional solidification in a cold crucible. All of the crystals consist of a mixture of two tetragonal phases of zirconia, t and t', differing in the degree of tetragonality (c/ $$\sqrt 2 a$$ ): 1.014–1.015 and 1.004–1.005 for the t- and t'-phases, respectively. All of the crystals have high microhardness (13.5–15.0 GPa) and high fracture toughness (on the order of 6–7 MPa m1/2). Their fracture toughness decreases with an increase in the total content of the stabilizing oxides, which is well consistent with the associated changes in phase composition, namely, with the increase in the percentage of the (transformable) t-phase. All of the crystals are similar in electrical conductivity: on the order of 0.04 S/cm at a temperature of 1173 K.

We have studied the structure, phase composition and mechanical properties, e.g. microherdness and impact toughness of partially stabilized zirconia crystals in the 2–4 mol.% stabilizing yttria concentration range. We have shown that with increasing concentration of stabilizing yttria the microhardness increases while the impact fracture toughness varies nonmonotonically and reaches the maximum for the partially stabilized zirconia crystal with 3 mol.% Y2O3. The anisotropy of the microhardness and impact fracture toughness was studied for wafers perpendicular to the 〈100〉, 〈110〉 and 〈111〉 directions with different indenter diagonal orientations. We have shown that the microhardness of the partially stabilized zirconia crystals depends but slightly on crystallographic orientation whereas the impact fracture toughness differs between crystallographic faces of the crystals. The highest impact toughness was obtained for the {100} plane and the indenter diagonal aligned parallel to the 〈100〉 direction, while the lowest impact toughness was obtained for the {110} plane and the indenter diagonal aligned parallel to the 〈110〉 direction. Local Raman study of the monoclinic phase distribution in the vicinity of the indentation shows that the maximum quantity of the monoclinic phase forms along the 〈110〉 direction regardless of indenter diagonal orientation. We have shown that the strain anisotropy during the phase transition has variable effect on crack impedance. The effect of transformation hardening mechanism depends on crack plane orientation and transition induced stress.

This work is a study of the effect of co-doping (ZrO2)0.9(Sc2O3)0.1 solid solution with yttria and/or ceria on the phase composition, local structure and transport properties of the crystals. The solid solution crystals were grown using directional melt crystallization in cold crucible. We show that ceria co-doping of the crystals does not stabilize the high-temperature cubic phase in the entire crystal bulk, unlike yttria co-doping. Ceria co-doping of the (ZrO2)0.9(Sc2O3)0.1 crystals increases their conductivity, whereas the addition of 1 mol.% yttria tangibly reduces the conductivity. Equimolar co-doping of the (ZrO2)0.9(Sc2O3)0.1 crystals with ceria and yttria changes the conductivity but slightly. Optical spectroscopy of the local structure of the crystals identified different types of optical centers. We found that the fraction of the trivalent cations having a vacancy in the first coordination sphere in the ceria co-doped crystals is smaller compared with that in the yttria co-doped crystals. Keywords: Single crystals, Solid oxide fuel cell, Solid solutions, Ionic conducting materials, ZrO2-Sc2O3-CeO2-Y2O3

Phase stability and transport characteristics of (ZrO2)1-x(Sc2O3)x(СeO2)y (x = 0.08–0.10; y = 0.005–0.015) and (ZrO2)1-x-y-z(Sc2O3)x(СeO2)y(Y2O3)z (x = 0.08–0.10; y = 0.005–0.010; z = 0.005–0.020) melt-grown crystals have been studied after air heat treatment at 1000 °C for 400 h. Annealing of the (ZrO2)1-x(Sc2O3)x(СeO2)y crystals caused the formation of a rhombohedral phase and reduced the electrical conductivity of the specimens in the entire test temperature range. Yttrium co-doping of the (ZrO2)1-x(Sc2O3)x(СeO2)y crystals stabilized the cubic phase for some compositions. In two-phase (ZrO2)1-x-y-z(Sc2O3)x(СeO2)y(Y2O3)z crystals containing a cubic and a tetragonal phases exhibited conductivity degradation. Annealing of cubic crystals caused the formation of the t'` phase and increased their conductivity.

The study focuses on corrosion fatigue processes taking place in an ultrafine-grained (UFG) near-α-titanium alloy Ti-2.5Al-2.6Zr (Russian industrial name PT7M) used in nuclear engineering. UFG structure formed with Rotary Swaging is found to increase resistance to corrosion fatigue. Parameters of the Basquin's equation are defined and the slope of the fatigue curve σa-lg(N) is shown to depend (nonmonotonic dependence) on the UFG alloy annealing temperature. This effect can be explained with the patterns of microstructural evolution in a UFG alloy PT7M during annealing: (1) reduced density of lattice dislocations, (2) precipitation and dissolution of zirconium nanoparticles, (3) release of α′′-phase particles causing internal stress fields along interphase (α-α′′)-boundaries, and (4) intensive grain growth at elevated annealing temperatures. It is shown that the fatigue crack closure effect manifested as changing internal stress fields determined using XRD method may be observed in UFG titanium alloys.

The research aims to analyze the impact that severe plastic deformation arising during Rotary Swaging has on mechanical properties and corrosion resistance of a near-α-titanium alloy Ti-2.5Al-2.6Zr (Russian industrial name PT7M). The nature of corrosion decay in fine-grained alloys caused by hot salt corrosion is known to vary from pit corrosion to intercrystalline corrosion at the onset of recrystallization processes. Resistance to hot salt corrosion in a fine-grained titanium alloy Ti-2.5Al-2.6Zr is shown to depend on the structural-phase state of grain boundaries that varies during their migration as a result of “covering” corrosive doping elements (aluminum, zirconium) distributed in the crystal lattice of a titanium alloy.

Polycrystalline thermoelectric elements of n-type Bi2(Te0.95Se0.05)3 and p-type (Bi0.25Sb0.75)2Te3 were fabricated by modified Bridgman technique, followed by electrospark cutting. A thermoelectric micromodule, consisting of 12 legs with an Ni anti-diffusion barrier and high-temperature SnSb solder between them, was assembled. To investigate thermoelements under conditions close to operating ones, the micromodule was annealed at 443 K for 1000 h. It was revealed that after annealing for more than 40 h, the near-contact zone of the n-type legs degraded, leading to a complete break of the micromodule junctions. Our results revealed that during annealing, the SnSb solder flowed into the unprotected side surface of the legs, and contacted with the cleavage planes along which tin can diffuse into the thermoelement volume. In contrast, the p-type legs were not affected by the contact with the solder. Different impacts of the solder on n- and p-type legs were explained in the framework of density functional theory (DFT) calculations. Substitution, diffusion and thermodynamic stability calculations showed that Bi to Sn substitution is energetically more beneficial than Sb to Sn substitution. Additionally, it was calculated that for the Bi2Te3 + Sn system, it is more beneficial to form a TeSn and Bi phase, while an Sb2Te3 + Sn system is thermodynamically stable.

A bulk nanostructured material based on oxidized silicon nanopowder was fabricated using a spark plasma sintering technique. Structural investigations revealed that this material has the composition of ∼14 nm core Si granules inside an SiO2 shell. Photoluminescence measurements have shown that the emission spectra lie in the energy range of 0.6–1.1 eV, which is not typical of the emissions of the Si/SiO2 nanostructures reported in numerous papers. This result can be explained by the formation of energy states in the bandgap and the participation of these states in both electronic transport and photoluminescence emission. Annealing of the sample leads to a decrease in defect density, which in turn leads to quenching of the 0.6–1.1 eV photoluminescence. In this case ∼1.13 eV inter-band transitions in the Si core start to play a dominant role in radiative recombination. Thus, the possibility of controlling the photoluminescence emission over a broad wavelength range was demonstrated.

The article presents the issues of replacing leucosapphires in jeweled bearings of the axes of precision instruments with nanostructured crystals of partially stabilized zirconia. The statement is substantiated that doping with rare earth elements provides an improvement in the performance properties of precision instruments by improving the mechanical properties of bearing materials. The efficiency of doping of zirconia crystals with cerium and neodymium oxides is studied. It was found that doped crystals have increased plasticity, which provides an increase in the crack resistance of crystals. Special attention is paid to the issues of increasing the survivability of high-speed rotor bearings by replacing the thrust bearing of leucosapphire with nanostructured crystals of partially stabilized zirconia doped with cerium and neodymium. The efficiency of improving the mechanical properties is confirmed by the X-ray phase analysis of crystals. The phase composition is studied by Raman scattering and the lattice parameters are determined. The increased crack resistance of the thrust bearing is confirmed by tests performed using the kinetic microhardness method.

Mechanical properties of fine-grained Al-(1, 2, 3)%Zn alloys obtained by Equal Channel Angle Pressing were studied. The recrystallization activation energy was found to decrease with increasing Zn content. The Hall-Petch coefficient for the Al-Zn alloys was found to change nonmonotonously during annealing. An increased Zn concentration at the grain boundaries was shown to result in altering the creep and superplasticity mechanisms of the Al-Zn alloys. The corrosion rate of the Al-Zn alloys was found to depend on the annealing temperature nonmonotonously. The corrosion rate in the Al-(2,3)%Zn alloy was shown to decreasing down to 8–9 mm/year with increasing the annealing temperature up to 200 оC. The increasing of the annealing temperature up to 300 оC leads to the increasing of the corrosion rate up to 11.4–11.9 mm/year. The obtained results were analyzed on the base of a concept of solid phase wetting of the grain boundaries in the Al by Zn. The effect of solid state wetting of the grains boundaries was shown to allow explaining majority of anomalia observed in the Al-Zn alloys: (i) the effect of the reduction of the recrystallization activation energy; (ii) the effect of a non-monotonous variation of the Hall-Petch coefficient during annealing; (iii) an increasing of plasticity of the Al-Zn alloys in the creep regime, etc. In order to describe the anomalia in the corrosion resistance of the Al-Zn alloys, one should also take into account a nonuniform Zn distribution in the specimens.

The size and morphology of Ti3Ni4 precipitates, as well as their transformation behavior after isothermal aging, were studied in a Ti-50.7 аt.%Ni shape memory alloy with various B2 austenite grain sizes. A 0.3 mm thick band with an accumulated strain of e = 44% (e = 0.6) obtained by cold rolling was used. The samples were then solution-treated at 600–800°С for 0.3–1 h with subsequent quenching in water to obtain the structure with different grain size (GS) from 5 to 15 μm. The samples were then subjected to isothermal annealing at 430 °C for 1, 3 and 10 h. The SEM observations were carried out using a JSM-6460LV. The microstructure was studied using a JEOL 2100 TEM. Characteristic temperatures were measured using a “Mettler Toledo” DSC. The results of the microstructure study prove that the GS strongly affects Ti3Ni4 particle size and morphology, as well as the degree of microscale microstructure heterogeneity, transformation kinetics and transformation sequences. This influence is non-unique and depends on the duration of isothermal annealing. After 1 h of aging, the particle thickness and diameter maintain the nanometer range in the whole GS range of 5–15 μm. The increase of aging time to 3 and 10 h leads to localization of nanosized precipitates in the grain-boundary region, with the width of these regions decreasing with increasing GS. After aging for 1 h, the samples with the GS of 5 μm show the B2→R transformation. The increase in the GS to 15 μm and aging duration to 10 h is accompanied by multiplication of martensitic transformations to four stages. The study explains the influence of GS on the precipitated particle size and morphology, transformation kinetics and staging.

Aluminum-based metallic glasses are the new promising family of materials. However, the effect of heat treatment on the structure and properties of Al–Y–Ni–Co amorphous alloys has not been widely studied so far. In this paper, Al85Y8Ni5Co2 amorphous alloy strips were obtained by hardening on a rotary copper wheel. The effect of vacuum annealing at temperatures ranging from 100 to 500 °C for 30 minutes on the structure and hardness of these strips was investigated. Transmission electron microscopy, X-ray diffraction analysis, and differential scanning calorimetry were used to study changes in the structure of strips after heat treatment. Vickers microhardness was measured to investigate the effect of annealing on the mechanical properties of strips. The results obtained allowed for the conclusions made about changes in hardness depending on the Al85Y8Ni5Co2 alloy strip structure. It was found that as the temperature rises, strip microhardness increases reaching a maximum value of 575±7 HV after annealing at 350 °C, then it decreases with a further increase in the annealing temperature. It was shown that the Al85Y8Ni5Co2 alloy strips remain completely amorphous and no crystalline phases are detected in their structures after annealing at temperatures up to 250 °C for 30 minutes. A sharp increase in hardness after annealing at 350 °C is associated with 10–30 nm nanocrystals of an aluminum solid solution formed in the amorphous matrix and surrounded by a residual amorphous matrix, while further hardness decrease is associated with the increasing sizes of these crystals and Al3Y and Al19Ni5Y3 intermetallics formed in the structure.

An experimental and theoretical study of the process of the equal−channel angular pressing (ECAP) was performed to obtain a thermoelectric (TE) material based on bismuth telluride. A brief review of the mathematical modeling of the ECAP process is given. The influence of the ECAP design features and temperature modes on the process of plastic forming is considered. The results of calculations of the thermally stressed state of samples at different stages of the ECAP process are presented. The calculations of the ECAP process were carried out by means of Lagrangian finite element mesh, which adjusted adaptively during the process to the die geometry and became finer or coarser depending on the magnitude of the plastic deformation. It was required for the specified calculation accuracy and the convergence of iterative process. The results of an experimental study of the structure and properties of samples obtained by the ECAP using a set of measuring methods (X−ray diffractometry and electron microscopy) are discussed. The thermoelectric characteristics of the obtained materials were measured by Harman method. Comparative methodical calculations of the ECAP process for TE materials based on bismuth telluride have been made by adjusting parameters determining the grain formation (i.e. the critical plastic deformation as a function of temperature and power−law dependence of its rates). It made possible to adjust the ECAP model on the basis of the measured grain sizes for TE materials . The calculation results of grain creation during the plastic forming, which are compared with the measurement data, are presented. The practical result of this research was the improved geometry of the die and the validated technological regimes of plastic deformation, which allowed obtaining samples with the good TE efficiency.

The anisotropy of the mechanical properties of single crystal ZrO2 — 2.8 mol.% Y2O3 solid solutions has been studied. The crystals have been grown by skull melting technique. The microhardness and fracture toughness have been tested for different crystallographic planes by indentation with different indenter diagonal orientations. The study shows that the microhardness of the material depends on the crystallographic orientation but slightly whereas the fracture toughness varies for different planes. The maximum fracture toughness has been observed in the crystal specimen cut laterally to the orientation. We have studied the anisotropy of the microhardness in the material for different indenter diagonal orientations. The maximum fracture toughness has been obtained for the {100} plane and the indenter diagonal orientation. The phase composition inside and outside the indents on the {100}, {110} and {111} surfaces for 20, 3 and 1 N loads has been studied in local areas using Raman spectroscopy. The degree of the tetragonal−monoclinic transition has been evaluated for different crystallographic planes and different indenter diagonal orientations. The tetragonal−monoclinic transition proves to be anisotropic, and this affects the transformation hardening mechanism. The maximum amount of the monoclinic phase is present in the vicinity of the indent in the {100} plane for the indenter diagonal orientation. The highest fraction toughness has also been observed in the {100} plane for the indenter diagonal orientation. Probably, the abovementioned indenter diagonal orientation provides for the maximum stress concentration along the coherent conjugation planes between the tetragonal and the monoclinic phases during the tetragonal−monoclinic transition, i.e. (100)t||(100)m and [001]t||[010]m.

Crystallization of metallic glasses produced by rapid solidification and supercooled liquids on heating takes place at large undercooling which has some peculiarities compared to crystallization on casting. By using transmission electron microscopy we present a detailed in-situ study of an unusual isothermal crystallization reaction observed in the Al85Y8Ni5Co2 metallic glassy alloy below Tg. It started from the formation of a primary intermetallic compound (IMC) immediately followed by a pseudo-eutectic reaction consisting of IMC and nanoscale Al (solid solution) particles while α-Al particles are significantly smaller in size than the intermetallic phase. Moreover, a majority of these nanoscale α-Al particles do not have a common interface with the primary IMC particles but are separated by the residual glassy phase which remains present within these pseudo-eutectic colonies. On the other hand, as can be assumed from the Gaussian type of the heat flow plot at the isothermal conditions and reasonable linearity of the Avrami plot this reaction takes place like a single stage process. This residual glassy phase has a high stability versus crystallization and crystallizes only at a higher temperature. However, such a crystallization mechanism is observed only on slow heating or isothermal exposure at a temperature below Tg. On rapid heating or at isothermal annealing in the supercooled liquid, primary nanocrystallization of the aluminum solid solution is observed followed by the formation of intermetallic compounds at a higher temperature.

A glassy phase is formed over the whole composition range for melt-spun (Fe1−xNix)79B12P5Si3C1 with x = 0; 0.2; 0.4; 0.5; 0.6 alloy ribbons and these glassy ribbons exhibit good bending plasticity. The Ni-containing glassy alloys show glass transition, followed by a supercooled liquid (SCL) region and then multistage crystallization for the alloys with x = 0.5 and 0.6 (hereafter 0.5Ni and 0.6Ni alloys). The 0.5Ni glassy alloy exhibits the largest SCL region of 43 K and good soft magnetic properties even in as-spun state, i.e., low coercive force of 4.8 A/m, effective permeability of 7400 at 1 kHz and saturation magnetization of 0.80 T. The bending plasticity remains unchanged in the wide annealing temperature range below Tg. The crystallization proceeds in the processes of glassy (G) → bcc(α)Fe(Si) + Fe3B for the 0–0.2 Ni alloys, G → fcc(γ)(Fe,Ni) + Fe3(B,C) + Fe3Ni3(B,C) for the 0.4Ni alloy and G → G’ + γ(Fe,Ni) → γ(Fe,Ni) + Ni5P2 + Fe4P + Fe3Ni3(B,C) for the 0.5Ni and 0.6Ni alloys. Analyses of crystallization reaction in isochronal and isothermal conditions were performed via Kissinger and JMAK models and the activation energy for crystallization is much larger for the 0.5Ni glassy alloy. The appearance of the largest SCL region as well as the highest activation energy for the 0.5Ni alloy is due to the necessity of the simultaneous decomposition to the four crystalline phases. The better magnetic softness for the 0.5Ni alloy is presumably due to the development of medium-range ordered atomic configurations which enable the appearances of the largest SCL region as well as the lower internal stress state. The combination of useful properties for the 0.5Ni glassy alloy is promising for useful soft magnetic materials with mass production ability.

Effects of equal-channel angular pressing (ECAP) with subsequent aging on the microstructure and phase transformation of Al–Mg2Si alloys with combined (Sc + Zr) and (Sc + Hf) additions were studied. The microstructure processed by ECAP and the precipitation of phases of Al–Mg2Si alloys were thoroughly examined by transmission electron microscopy (TEM). An analysis of the precipitation and determination of the temperatures of these precipitations in Al–Mg2Si alloys after ECAP was carried out by DSC. It has been revealed that transition metals added to Al–Mg2Si alloys do not change the character of decomposition of the solid solution but shift the precipitation temperatures of the β'', β' and β phases to lower temperatures compared to the quenched state. Recovery processes have been revealed in the temperature range 200–600 °C based on the changes in hardness and electrical resistivity of Al–Mg2Si alloys with additions of transition metals (Sc + Zr) and (Sc + Hf) and without them after ECAP.

The research has been conducted into the impact that structural-phase state of grain boundaries in α-titanium alloy Ti-5Al-2V has on strength, plasticity and susceptibility to intercrystalline corrosion (ICC). It is found that during Equal Channel Angular Pressing (ECAP) performed at elevated temperatures there is a change in local concentration of alloying elements (aluminum, vanadium) along α-Ti grain boundaries. The current study proves that by controlling the structure of α-titanium alloy Ti-5Al-2V through ECAP it is possible to enhance its strength and resistance to hot salt intercrystalline corrosion. Plasticity of ultrafine-grained (UFG) alloy samples at room temperature is comparable with plasticity of a coarse-grained material, while plasticity of an UFG alloy at elevated temperatures is 2–3 times bigger than plasticity of a coarse-grained material.

The effect of Sc on plasticity at elevated temperatures(from 300 to 500 °C) and strain rates(from 10−3 to 10−1 s−1)of ultrafine-grained (UFG) Al–0.5%Mg–Sc alloyswas investigated. In the UFG alloys with 0.4% and 0.5%Sc at 500 °C and strain rate 1·10−1 s−1, high elongation to failure (~1060%) was achieved. The fractographic analysis of the fracturesin the Al–0.5%Mg alloy demonstrated the crack growth zone to occupy almost whole fracture area.The self-destruction in the crack growth zone has a viscous character.In the UFG alloys with Sc, numerous pits formed as a result of micropore junction were observed. Dependencies of dynamic grain growth (DGG) rate on the temperature and strain rate were determined. The DGG in the Al–0.5%Mg–Sc alloys was found. The kinetics of the DGG in the Al–0.5%Mg–0.2%Sc alloy was shown to be limited by mobility of junction disclinations. In the Al–0.5%Mg–0.5%Sc alloy, it is limited by mobility of oriented misfit dislocations. Al3Sc particles were shown to be possible origin of the micropore formation and of accelerated destruction of the Al–0.5%Mg–Sc alloys at high temperature deformation.

The article analyzes the effect of the addition of iron in the Zr–Cu–Al system metallic glassy alloys on the phase separation process during thermo-mechanical treatment. The addition of Fe causes formation of nanostructured regions of chemical inhomogeneity after cold rolling and annealing below the glass transition temperature. The resulted effect on the mechanical properties of the investigated alloys is established. Changes in the structure during thermo-mechanical treatment are studied in detail by transmission electron microscopy. The increase in the microhardness of the alloys during the formation of inhomogeneities in the amorphous matrix is explained by the difficulty of propagation of the shear bands formed during deformation.

We have prepared and characterized lithium titanate-based anode materials, Li4Ti5O12/C and Li4Ti5O12/C/Ag, using polyvinylidene fluoride as a carbon source. The formation of such materials has been shown to be accompanied by fluorination of the lithium titanate surface and the formation of a highly conductive carbon coating. The highest electrochemical capacity (175 mAh/g at a current density of 20 mA/g) is offered by the Li4Ti5O12-based anode materials prepared using 5% polyvinylidene fluoride. The addition of silver nanoparticles ensures a further increase in electrical conductivity and better cycling stability of the materials at high current densities.

In this work, mathematical modeling was used to optimize the geometry of the composite mold for developing the technology of equal−channel angular pressing with three channels for thermoelectric materials. To obtain the maximum degree of deformation in this work, we used a three−channel scheme. Taking into consideration the material characteristics (low resistance to tensile stresses), we proposed a tapering profile (along the length) of the third channel. To analyze the plastic flow in the proposed scheme of equal−channel angular pressing with three channels, we performed mathematical modeling of plastic flow, stress and deformation rates along the rod, deformation homogeneity along the cross−section and absence of stagnant zones in the extruder. The methodical approach is based on the combined use of the elastic and plastic solid state approximations according to the fundamentals of the elasticity and plasticity theory. Critical points are identified having the maximum stored energy accumulation without discontinuity of the material. Calculation of the flow velocity in planes perpendicular and parallel to the deformation axis showed a slight difference in the flow rate of the material for the section plane parallel to the deformation axis. This produces a bend with a large curvature radius but does not cause cracking of the material. Calculation of deformations along the flow axis allowed us to detect deformation inhomogeneity. This resulted in the appearance of small tensile stresses in the longitudinal section of the third channel. We show that the plastic deformation inhomogeneity revealed by modeling can be eliminated by using an equipment design with a greater output channel length. Mathematical modeling shows the suitability of the suggested unconventional design of equal−channel angular pressing equipment for bismuth chalcogenide base solid solutions.

We have studied the influence of the yttrium oxide (Y2O3) dopant (1 and 2 mol %) on the phase composition, structure, and electrical properties of ZrO2–9 mol % Sc2O3 solid solution. Stabilization of ZrO2 jointly with 9 mol % Sc2O3 and 2 mol % Y2O3 is shown to allow the acquisition of high phase stability transparent homogeneous crystals with a cubic structure. Their mechanical grinding is established to cause no change in the phase composition of these crystals, whereas the powders retain the initial fluorine structure. The powders preserved the original structure of the fluorite crystals. All the probed crystals reveal high microhardness and low fracture toughness. Increasing the Y2O3 concentration in the crystals led to a reduction of the maximum loads on the indenter, which the sample withstood without cracking. As is shown, the specific conductivity exhibits nonmonotonic behavior depending on the Y2O3 concentration in the crystals. Increasing the Y2O3 content to 2 mol % in the solid electrolyte reduces the conductivity of the crystals in the entire temperature range that is attributed to a decrease in the carrier mobility due to the increasing ion radius of the stabilizing ion.

The influence of homogenisation regimes on precipitations of fine Mn-bearing dispersoids, recrystallisation kinetics, grain structure, mechanical properties and superplasticity of cold worked sheets of Al-3Mg alloys with Mn, Cr and Zr is studied. Precipitates of coherent compact and plate-like particles of Mn-bearing phase are found after homogenisation annealing. Activation parameters of the low-temperature internal friction, internal friction solute grain boundaries peak and dislocation nature thermally activated relaxation peak in the samples treated by different regimes are compared. High-temperature homogenisation at 460 °C provides a higher volume fraction and finer particles of Mn-containing phases after thermomechanical processing compared to low temperature treatment at 380 °C. Consequently, finer grains and higher superplasticity indicators are achieved in a recrystallised state. Polygonisation is observed during heating of the cold worked samples pre-homogenised at 380 °C: recrystallisation temperature is increased and mechanical strength at room temperature is improved. Keywords: Aluminium alloys, Precipitations, Recrystallisation, Internal friction, Superplasticity

The data presented in this article are related to the research article entitled “Phase stability and transport characteristics of (ZrO(2))(1-x)(Sc(2)O(3))(x)(СeO(2))(y) and (ZrO(2))(1-x-y-z)(Sc(2)O(3))(x)(СeO(2))(y)(Y(2)O(3))(z) solid solution crystals” https://www.sciencedirect.com/science/article/pii/S2352340917302329 [1]. It contains data on densities and microhardness of the as-grown crystals. The data on the specific conductivity of the as-grown and annealing at 1000 °С for 400 h ScCeSZ and ScCeYSZ crystals in the temperature range 623–1173 K is also included in this article. The article describes also the growth of the (ZrO(2))(1-x)(Sc(2)O(3))(x)(СeO(2))(y) and (ZrO(2))(1-x-y-z)(Sc(2)O(3))(x)(СeO(2))(y)(Y(2)O(3))(z) solid solution crystals using directional melt crystallization in a cold crucible.

Low plasticity is a key drawback limiting the widespread use of bulk metallic glasses. Although heat treatment and thermo-mechanical processing techniques are not applied to metallic glasses (only to supercooled liquids), since heating leads to embrittlement either due to structural relaxation or thermal crystallization, in this paper, we demonstrate a strong positive effect of cold rolling and subsequent thermal annealing below the glass-transition temperature on room-temperature mechanical properties of a Zr62·5Cu22·5Fe5Al10 glassy alloy. As a result we observed mechanical softening and appearance of tensile ductility (up to 1.5%) in bulk samples and an increase in hardness by up to 25% in ribbon samples yet retaining good bending plasticity. We believe that the proposed method can be applied to a number of metallic glasses.