Grain boundary segregation in UFG alloys processed by severe plastic deformation

Grain boundary segregations were investigated by Atom Probe Tomography in an Al-Mg alloy, a carbon steel and Armco\trademark Fe processed by severe plastic deformation (SPD). In the non-deformed state, the GBs of the aluminium alloy are Mg depleted, but after SPD some local enrichment up to 20 at.% was detected. In the Fe-based alloys, large carbon concentrations were also exhibited along GBs after SPD. These experimental observations are attributed to the specific structure of GBs often described as "non-equilibrum" in ultra fine grained materials processed by SPD. The grain boundary segregation mechanisms are discussed and compared in the case of substitutional (Mg in fcc Al) and interstitial (C in bcc Fe) solute atoms

Предпосылки применения просвечивающей электронной микроскопии как геохимической методики выявления миграционных минеральных форм над углеводородными залежами

Актуальность исследования обусловлена необходимостью разработки методики нахождения и определения миграционных форм металлических соединений над контурами углеводородных залежей на поверхности Земли, так как существующая в настоящее время информация о возможности переноса металлов с уровня залежи зачастую противоречива, что ставит под сомнение саму возможность геохимических поисков углеводородных залежей на основе информации о содержании металлов в приповерхностных горизонтах. Обсуждаемая методика сбора и анализа позволяет изучать наноразмерные соединения металлов, мигрирующих в составе газового потока до поверхности Земли. Появляется возможность установления происхождения найденного наноразмерного металлического соединения с допустимостью доказать глубинную природу происхождения вещества, найденного на дневной поверхности. Цель работы: обзор и анализ существующих знаний о геохимических методах поисков месторождений нефти и газа; моделирование новой геохимической методики, связанной с исследованием образцов на просвечивающем электронном микроскопе, с возможностью установления частиц в наноразмерном состоянии. Методы исследования: геохимические методы поиска и разведки месторождений нефти и газа, просвечивающая электронная микроскопия. Результаты. Проведен обзор и анализ литературы на тему геохимических методов поисков залежей нефти и газа, проанализированы закономерности особенностей геохимических полей над месторождениями нефти и газа Западно-Сибирской нефтегазоносной провинции. Предложена новая геохимическая методика поисков и разведки, которая способна выявлять минеральные формы нахождения химических элементов в наноразмерном состоянии на просвечивающем электронном микроскопе, в частности находить и идентифицировать миграционные металлические соединения.The relevance of the discussed issue is caused by the necessity to develop the technique for finding and identifying metal compounds migration forms over the boundaries of hydrocarbon deposits on the Earth surface. The existing information on possibility of metal transfer from the level of deposits is often contradictory and it can cast doubt on the possibility of geochemical prospecting of hydrocarbon deposits on the basis of information on metal content in the subsurface horizons. The technique of collection and analysis allows us to study nanoscale metal compounds migrating as a part of gas flow to the Earth surface. It becomes possible to determine the origin of nanoscale metal compounds with the ability to prove the genesis of the deep nature of the substance found on the surface. The main aim of the research is to review and to analyze the existing knowledge on geochemical methods of prospecting for oil and gas; to model a new geochemical method associated with the study of samples on a transmission electron microscope for identifying nanoscale particles. The methods used in the study: geochemistry methods of prospecting and exploration of oil and gas fields, transmission electron microscopy. The results of the research. The authors have reviewed and analyzed the literature on geochemical methods to search for oil and gas deposits and analyzed the patterns of geochemical features and magnetic fields on deposits of the West Siberian oil and gas province. The paper introduces a new prospecting and exploration geochemical and magnetic technique which can help identify nanoscale mineral forms of chemical elements with a transmission electron microscope, in particular find and identify migration metal compounds

Using Severe Plastic Deformation to Produce Nanostructured Materials with Multifunctional Properties

Использование прецизионных методов структурного анализа (TEM/HRTEM, 3D APT и других) показало, что формирование разных типов границ зерен значительно влияет на механические свойства наноструктурных металлов и сплавов, особенно на хрупкость и пластичность, усталость и сверхпластичность. Затронуты вопросы использования зернограничной инженерии для создания наноматериалов, обладающих сочетанием высоких механических и функциональных свойств (коррозионная и радиационная стойкость, электропроводность и т. д.). Обсуждаются физическая природа данных необычных свойств наноматериалов и их применение в инновационных разработках.It has been shown by using the precise methods of structural analysis (TEM/HRTEM, 3D APT and others) that the formation of different types of grain boundaries significantly affects the mechanical properties of nanostructured metals and alloys, especially embrittlement and ductility, fatigue and superplasticity. The issues of using grain boundary engineering to create nanomaterials with socalled multifunctional properties obtaining a combination of high mechanical and functional properties (corrosion and radiation resistance, electrical conductivity, etc.) are considered. The physical nature of these unusual properties of nanomaterials and their application in innovative developments to use in the energy, medicine and engineering sectors is discussed

Archaeological survey of wooden remains from 16th-19th century Sviyazhsk

This article is devoted to the results of an archaeological survey carried out in 2008 on the site of the former faubourg (suburb) of Sviyazhsk town. The survey obtained and analysed useful information about the nature and contents of the cultural layer being revealed by the eroding banks of the Kuibyshev reservoir. The survey represented the first archaeological research carried out in the Sviyazhsk faubourg, and yielded much information on its layout. The remains of approximately 40 wooden constructions (buildings, fences, pavements, etc.) from the second half of the 16th-beginning of the 20th century were uncovered during the excavation. The residential character of the excavated buildings was determined by the presence of furnace remains found on the excavation site. The unified orientation of the household buildings from various layers of the excavation site, dating from the mid-16th up to the 20th century, indicates the street plan of the faubourg, which was more or less maintained throughout its existence. More than half the studied constructions were damaged by fire which accordingly gave rise to the development of the Sviyazhsk faubourg. The finds - 5,374 items in total - included 2,863 ceramic fragments (of which 334 were of traditional Bulgar style); 2,391 leather items (shoes, mittens, quivers, etc.); textiles (wool, homespun linen, felt, willow fibre) and iron goods (knives, scissors, nails, etc.). The numerous finds that emerged from the excavation site reflect the life, craft, farming and trading activities of the population of this medieval town and concurred with other known sources illustrating the life of Sviyazhsk residents as the town waxed and waned in its political importance as a trading post and economic centre of the region

NANOSTRUCTRAL DESIGN OF METALLIC MATERIALS FOR ENHANCING THEIR MULTIFUNCTIONAL PROPERTIES

Nanostructuring of metals and alloys by methods of intensive plastic deformation (IPD) can significantly increase the mechanical and functional properties of materials. It is shown that the use of different modes and routes of IPD processing during the formation of nanostructured metals and alloys significantly affects their mechanical properties, especially brittleness and ductility, fatigue and superplasticity.Наноструктурирование металлов и сплавов методами интенсивной пластической деформации (ИПД) может значительного повышать механические и функциональные свойства материалов. Показано, что использование разных режимов и маршрутов ИПД обработки при формировании наноструктурных металлов и сплавов значительно влияет на их механические свойства, особенно, хрупкость и пластичность, усталость и сверхпластичность.Исследование было частично поддержано Министерством науки и высшего образования Российской Федерации в рамках проекта №14.586.21.0061 (уникальный идентификатор проекта RFMEFI58618X0061)

High-Pressure torsion-Induced Grain Growth in Electrodeposited Nanocrystalline Ni

Deformation-induced grain growth has been reported in nanocrystalline (nc) materials under indentation and severe cyclic loading, but not under any other deformation mode. This raises an issue on critical conditions for grain growth in nc materials. This study investigates deformation-induced grain growth in electrodeposited nc Ni during high-pressure torsion (HPT). Our results indicate that high stress and severe plastic deformation are required for inducing grain growth, and the upper limit of grain size is determined by the deformation mode and parameters. Also, texture evolution suggests that grain-boundary-mediated mechanisms played a significant role in accommodating HPT strain

Microstructural changes and strengthening of austenitic stainless steels during rolling at 473 k

The microstructural changes in 304L and 316L austenitic stainless steels during plate rolling with 95% rolling reduction at a temperature of 473 K and their effect on strengthening were studie

Nanostructures in Ti processed by severe plastic deformation

Metals and alloys processed by severe plastic deformation (SPD) can demonstrate superior mechanical properties, which are rendered by their unique defect structures. In this investigation, transmission electron microscopy and x-ray analysis were used to systematically study the defect structures, including grain and subgrain structures, dislocation cells, dislocation distributions, grain boundaries, and the hierarchy of these structural features, in nanostructured Ti produced by a two-step SPD procedure-warm equal channel angular pressing followed by cold rolling. The effects of these defect structures on the mechanical behaviors of nanostructured Ti are discussed

Influence of severe plastic deformation on the precipitation hardening of a FeSiTi steel

The combined strengthening effects of grain refinement and high precipitated volume fraction (~6at.%) on the mechanical properties of FeSiTi alloy subjected to SPD processing prior to aging treatment were investigated by atom probe tomography and scanning transmission electron microscopy. It was shown that the refinement of the microstructure affects the precipitation kinetics and the spatial distribution of the secondary hardening intermetallic phase, which was observed to nucleate heterogeneously on dislocations and sub-grain boundaries. It was revealed that alloys successively subjected to these two strengthening mechanisms exhibit a lower increase in mechanical strength than a simple estimation based on the summation of the two individual strengthening mechanisms