STRUCTURE AND PROPERTIES OF LAYERED COMPOSITE MATERIALS BASED ON VT14 AND VT20 TITANIUM ALLOYS

В работе методом сварки взрывом были получены слоистые композиты на основе псевдо-α-титана ВТ20 и (α+β)-титана ВТ14. Была исследована структура полученных материалов на межслойных границах и определена степень деформационного упрочнения тонких слоев, прилегающих к границам раздела, путем измерения уровня их микротвердости.In this study layered composites based on a pseudo-α-titanium VT20 and (α + β)-titanium VT14 were obtained by the method of explosion welding. The structure of the obtained materials was investigated at the interlayer boundaries and the degree of strain hardening of thin layers adjacent to the interfaces was determined by measuring the level of micro-hardness

A novel operando approach to analyze the structural evolution of metallic materials during friction with application of synchrotron radiation

In this study, we describe an experimental setup and a new approach for operando investigation of structural evolution of materials during wear and friction. The setup is particularly suited for testing various friction pairs, including those in which both rubbing bodies are made of metals. The developed device allows circumventing the problems related to significant scattering of X-rays produced by metals and makes it possible using “real samples” in synchrotron beamlines operating in reflection mode. To demonstrate the capabilities of the device and the proposed new approach, an iron-based massive sample was subjected to thousands of friction cycles using a cemented carbide pin. The material was probed with synchrotron X-ray radiation within a few milliseconds after leaving the friction zone. The results of the microstructural and structural analysis, as well as results obtained from diverse mathematical models, allowed us to evaluate several features, including gradual accumulation of defects, microstructural refinement, dislocation density changes, surface layer oxidation, as well as several other phenomena caused by the dry sliding friction process. Mainly, it was possible to conclude that the process of wear occurred due to the cooperative action of oxidation and plastic deformation, which began during the first cycle of frictional interaction and was manifested in increasing the dislocation density, whose type was changed gradually during testing. The number of defects quickly reached a threshold value and subsequently fluctuated around it due to periodically repeated processes of defect accumulation and stress relaxation resulting from material wear. It was also observed that friction led to the quick formation of a mechanically mixed layer, consisting of the sample material and a mixture of two types of iron oxide – hematite and magnetite. The delamination of this layer was probably the primary wear mechanism

Stabilization of Ti5Al11 at room temperature in ternary Ti-Al-Me (Me = Au, Pd, Mn, Pt) systems

Ti$_5$Al$_{11}$ is known as a high-temperature phase in binary Ti-Al alloys. However, its existence at low temperatures was previously observed in ternary Ti-Al-based systems alloyed with some transition metals. In this study, we systematically evaluated Ti-Al-Me ternary systems (Me = Au, Pd, Mn, or Pt) to determine the influence of transition elements on low-temperature stabilization of Ti$_5$Al$_{11}$ phase. The temperature ranges in which Ti$_5$Al$_{11}$ existed in Ti-Al-Me systems were experimentally found using in situ synchrotron X-ray diffraction (SXRD). It was established that addition of Mn and Pt retains Ti$_5$Al$_{11}$ at room temperature. The obtained data were compared with predictions of density functional theory (DFT). The total energy, volume, and bond length are especially significantly reduced by addition of Mn and Pt. Ti5Al11 compound containing both of these elements is less prone to saturation with Ti upon preserving the lattice tetragonality and suppressing Ti$_5$Al$_{11}$ → TiAl transformation. These factors finally contribute to the retention of this phase at room temperature

Joining Ti-based metallic glass and crystalline titanium by magnetic pulse welding

Due to low thermal stability and limited critical size, metallic glasses (MGs) are frequently considered for reinforcing composites. The production technology of composites should provide the minimum heat input to preserve the disordered structure of MGs. In this study, the solid-state magnetic pulse welding (MPW) was used to join crystalline titanium and Ti-based MG. The amorphous structure of the MG layer after MPW was confirmed by synchrotron X-ray radiation diffraction (XRD), ultra-small-angle X-ray scattering (uSAXS), and transmission electron microscopy (TEM). Crystalline particles were found only in the mixing zones subjected to the strongest heating during welding. The average size of the crystalline precipitates was about 25 nm, and their phase composition corresponded to a-Ti. In addition to Ti particles, titanium oxides and nitrides could form at the interface of Ti and MG layers during MPW

THE FUNCTIONAL ACTIVITY OF INNATE IMMUNITY CELLS IN BACTERIAL INFECTION ON BACKGROUND OF THERMAL STRESS

Maintenance of thermo homeostasis under the coordinating influence of the hypothalamus is ensured by integrative interaction of various systems organisme, including the immune system. Temperature stress in infectious diseases activates the reaction of heat shock, the biochemical consequence of which is the initiation of the organism’s defense against the pathogen. Cells of innate immunity (neutrophils and macrophages) are the first line of protection against pathogenic agents and play a primary role in the development of bacterial infections. Of particular interest is the study of the duration of the effect of hyperthermia to achieve a balance between the bioenergetic costs of these cells, as well as the study of the course of the pathological process in an organism previously exposed to hige temperature. The functional status of neutrophils and macrophages, including phagocytosis, the activity of enzymes of the oxygen-dependent system: lactate dehydrogenase, cytochrome oxidase, myeloperoxidase, cellular stimulation (intracellular AMPase content) and the content of nitrogen oxide metabolites have been studied in the model of animals exposed to low and high temperatures. It has been established that under hyperthermia conditions, the change in the functional activity of cells by enzyme level is more pronounced than when exposed to animals with low temperature, especially 4 h exposure. In animals pre-exposed to heat stress, manifestations of pseudotuberculosis infection were more severe with an increase in mortality rates by 2.6 times, compared to animals infected by bacteria. These animals had a high stimulation of effector cells of inflammation in the initial periods (at 7 days) their metabolism was enhanced, which was expressed of the activity of enzymes of the oxygen-dependent system, as well as in high nitroxide-producing activity. In target organs (lung, liver, spleen) of experienced animals the severe disturbance of blood circulation in combination with significant destructive changes typical for generalized infection were showed. At dead animals on the background of marked hemorrhagic component pathological process and weak cell inflammatory response observed depletion of the immune system (delimphatization), indicating a decrease in defense reactions and the development of immunodeficiency. Thus, under conditions of heat stress (+30°С), the intensity of the reaction of innate immunity cells in terms of enzyme’s functional activity was higher than when exposed to animals of low temperature (+4°C). Under these temperature conditions, a high level of cell priming was determined, which reduced their killing potential. These data indicate the adequacy of the model used to reproduce induced secondary immunodeficiency in a congenital defense system. Moreover, in the pathogenesis of pseudotuberculosis infection against the background of prolonged action high temperature, the effects of phagocytes oxidative stress in the structural changes of immunocompetent organs were detected

Structure and Oxidation Behavior of NiAl-Based Coatings Produced by Non-Vacuum Electron Beam Cladding on Low-Carbon Steel

NiAl-based intermetallic coatings were obtained using non-vacuum electron beam cladding on low-carbon steel. The structure of the coatings was investigated using optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), electron backscatter diffraction (EBSD), and X-ray diffraction (XRD). The coatings mostly consisted of grains elongated perpendicular to the substrates, with a strong <100> texture along the grain growth direction. The coatings contained about 14 at. % Fe, which appeared due to the partial melting of the steel substrate. At the bottom of the coatings, an inhomogeneous mixing zone with an increased concentration of Fe was formed; at the “substrate–coating” interface, a thick layer with a Fe50-Ni25-Al25 at. % composition was observed. The samples exhibited weight gains of 0.1, 0.8, 2.14, and 3.4 mg/cm2 after 100 h of oxidation at 700, 800, 900, and 1000 °C, respectively. The oxide layer contained α-Al2O3 and θ-Al2O3, and the presence of iron atoms contributed to the formation of a small amount of spinel. During the oxidation process, a layer with a high Fe content (~60 at. %) formed along the boundary between the oxide film and the NiAl-based material, which had a positive effect on the formation of a non-porous “oxide–coating” interface