Effect of high-pressure torsion on structure and microhardness of ti/tib metal–matrix composite

Effect of high-pressure torsion (HPT) at 400 °C on microstructure and microhardness of a Ti/TiB metal–matrix composite was studied. The starting material was produced by spark plasma sintering of a mixture of a pure Ti and TiB2 (10 wt %) powders at 1000 °C. The microstructure evolution during HPT was associated with an increase in dislocation density and substructure development that resulted in a gradual microstructure refinement of the Ti matrix and shortening/redistribution of TiB whiskers. After five revolutions, a nanostructure with (sub) grain size of ~30 nm was produced in Ti matrix. The microhardness increased with strain attaining the value ~520 HV after five revolutions. The contribution of different hardening mechanisms into the hardness of the Ti/TiB metal–matrix composite was quantitatively analyzed

Effect of High-Pressure Torsion on Structure and Microhardness of Ti/TiB Metal–Matrix Composite

Effect of high-pressure torsion (HPT) at 400 °C on microstructure and microhardness of a Ti/TiB metal–matrix composite was studied. The starting material was produced by spark plasma sintering of a mixture of a pure Ti and TiB2 (10 wt %) powders at 1000 °C. The microstructure evolution during HPT was associated with an increase in dislocation density and substructure development that resulted in a gradual microstructure refinement of the Ti matrix and shortening/redistribution of TiB whiskers. After five revolutions, a nanostructure with (sub) grain size of ~30 nm was produced in Ti matrix. The microhardness increased with strain attaining the value ~520 HV after five revolutions. The contribution of different hardening mechanisms into the hardness of the Ti/TiB metal–matrix composite was quantitatively analyzed

Cracking Behavior of the ZhS6K Superalloy during Direct Laser Deposition with Induction Heating

For this work, the behavior of the ZhS6K alloy (Russian grade) in the process of direct laser deposition was investigated. Two samples, a “small” one (40 × 10 × 10 mm3) and “large” one (80 × 16 × 16 mm3), were fabricated with direct laser deposition. In both samples, the typical dual-phase γ/γ’ microstructure with cuboidal shape of the γ’ precipitates was observed. Both specimens revealed a similar tendency to continuous increasing in hardness from the bottom to the top associated with the refinement of γ’ precipitates. The “small” sample was essentially crack-free, while the “large” one underwent extensive cracking. The possible effects of various factors, including thermal history, size, and shape of the gamma grains, on cracking behavior were discussed

Mechanical Behavior of a Medium-Entropy Fe₆₅(CoNi)₂₅Cr_9.5C_0.5 Alloy Produced by Selective Laser Melting

Specimens of a medium-entropy Fe65(CoNi)25Cr9.5C0.5 (in at.%) alloy were produced using additive manufacturing (selective laser melting, SLM). The selected parameters of SLM resulted in a very high density in the specimens with a residual porosity of less than 0.5%. The structure and mechanical behavior of the alloy were studied under tension at room and cryogenic temperatures. The microstructure of the alloy produced by SLM comprised an elongated substructure, inside which cells with a size of ~300 nm were observed. The as-produced alloy demonstrated high yield strength and ultimate tensile strength (YS = 680 MPa; UTS = 1800 MPa) along with good ductility (tensile elongation = 26%) at a cryogenic temperature (77 K) that was associated with the development of transformation-induced plasticity (TRIP) effect. At room temperature, the TRIP effect was less pronounced. Consequently, the alloy demonstrated lower strain hardening and a YS/UTS of 560/640 MPa. The deformation mechanisms of the alloy are discussed

Microstructure and Mechanical Properties Evolution of the Al, C-Containing CoCrFeNiMn-Type High-Entropy Alloy during Cold Rolling

The effect of cold rolling on the microstructure and mechanical properties of an Al- and C-containing CoCrFeNiMn-type high-entropy alloy was reported. The alloy with a chemical composition (at %) of (20–23) Co, Cr, Fe, and Ni; 8.82 Mn; 3.37 Al; and 0.69 C was produced by self-propagating high-temperature synthesis with subsequent induction. In the initial as-cast condition the alloy had an face centered cubic single-phase coarse-grained structure. Microstructure evolution was mostly associated with either planar dislocation glide at relatively low deformation during rolling (up to 20%) or deformation twinning and shear banding at higher strain. After 80% reduction, a heavily deformed twinned/subgrained structure was observed. A comparison with the equiatomic CoCrFeNiMn alloy revealed higher dislocation density at all stages of cold rolling and later onset of deformation twinning that was attributed to a stacking fault energy increase in the program alloy; this assumption was confirmed by calculations. In the initial as-cast condition the alloy had low yield strength of 210 MPa with yet very high uniform elongation of 74%. After 80% rolling, yield strength approached 1310 MPa while uniform elongation decreased to 1.3%. Substructure strengthening was found to be dominated at low rolling reductions (<40%), while grain (twin) boundary strengthening prevailed at higher strains

Comparative analysis of reagents-inhibitors of swelling of clay deposits used in Eastern Siberia

Актуальность. Подсолевой структурный комплекс месторождений Восточной Сибири включает в себя отложения ордовика, которые представлены преимущественно супесями, суглинками, глинами, алевролитами, мергелями и доломитами. Подсолевой комплекс состоит из аргиллитов, доломитов, известняков, а также их переслаивания. При бурении нефтяных скважин большое количество осложнений может вызвать набухание глинистых пород: прихват бурильного инструмента, кавернообразование, сальникообразование, расширение ствола скважины, потеря циркуляции и др. Буровой раствор должен обладать высокой ингибирующей способностью для максимального снижения интенсивности набухания. Этого свойства можно добиться специальными реагентами-ингибиторами, которые являются основным компонентом ингибирующего бурового раствора. Цель: исследовать ингибирующую способность линейки реагентов, которые представляют композиции аминов, полиамидов и ряда других соединений. Объект: буровой раствор, применяемый на месторождениях Восточной Сибири. Методы. Для определения линейного набухания глины использовалась модель Linear Swellmeter OFITE, определяющая гидратирование или дегидратирование глин и глинистых пород путем измерения изменения линейных размеров образца из глины. Исследование по влиянию реагентов ингибиторов на реологические параметры бурового раствора проводилось с помощью традиционных методов. Результаты и выводы. Установлено, что соли MgCl*6H2O и NaCl, структурирующие молекулы воды, снижают набухание глинопорошка. Все исследуемые образцы ингибиторов в разной степени оказывают влияние на параметры бурового раствора, наиболее благоприятными для использования в пресном глинистом буровом растворе на основе бентонитовой немодифицированной глины оказались Ингидол Б и Ингидол Sil. Остальные образцы также могут успешно использоваться при дальнейшей обработке раствора для регулирования реологических параметров и показателя фильтрации после проведенных дополнительных исследований.The relevance. The subsalt structural complex of Eastern Siberian deposits includes Ordovician deposits, which are mainly represented by sandy loams, loams, clays, siltstones, marls and dolomites. The subsalt complex consists of mudstones, dolomites, limestones, as well as their intercalation. When drilling oil wells, a large number of complications can cause swelling of clay rocks: sticking of a drilling tool, cavern formation, gland formation, expansion of the wellbore, loss of circulation, etc. The drilling fluid must have a high inhibitory ability to minimize the swelling rate. The main aim of the research is to study the inhibiting property of reagents, which represent compositions of amines, polyamides and some other compounds. Object: drilling fluid used in the fields of Eastern Siberia. Methods. To define the linear swelling of clay the authors have used the Linear Swellmeter OFITE model, which determines the hydration or dehydration of clays and clay rocks by measuring the change in the linear dimensions of the clay sample. The effect of inhibitor reagents on drilling fluid rheological parameters was studied using traditional methods. Results. It was found that MgCl*6H2O and NaCl salts, which structure water molecules, reduce the swelling of clay powder. All the studied inhibitor samples to varying degrees affect the parameters of the drilling fluid, Ingidol B and Ingidol Sil were the most favorable for use in fresh clay drilling mud based on unmodified bentonite clay. The remaining samples can also be successfully used during further processing of the solution to control the rheological parameters and the filtration index after additional studies

<i>Listeria monocytogenes</i> ST37 Distribution in the Moscow Region and Properties of Clinical and Foodborne Isolates

Listerias of the phylogenetic lineage II (PLII) are common in the European environment and are hypovirulent. Despite this, they caused more than a third of the sporadic cases of listeriosis and multi-country foodborne outbreaks. L. monocytogenes ST37 is one of them. During the COVID-19 pandemic, ST37 appeared in clinical cases and ranked second in occurrence among food isolates in the Moscow region. The aim of this study was to describe the genomic features of ST37 isolates from different sources. All clinical cases of ST37 were in the cohort of male patients (age, 48–81 years) with meningitis–septicemia manifestation and COVID-19 or Influenza in the anamnesis. The core genomes of the fish isolates were closely related. The clinical and meat isolates revealed a large diversity. Prophages (2–4/genome) were the source of the unique genes. Two clinical isolates displayed pseudolysogeny, and excided prophages were A006-like. In the absence of plasmids, the assortment of virulence factors and resistance determinants in the chromosome corresponded to the hypovirulent characteristics. However, all clinical isolates caused severe disease, with deaths in four cases. Thus, these studies allow us to speculate that a previous viral infection increases human susceptibility to listeriosis