Раздел "Получение и анализ структуры материалов"

Superplastic behavior of nickel-based superalloys with ultrafine grain structure.

Established that at the increase of the mass fraction of carbon from 0.09% to 0.30% in the as-cast metal, the metal hardness increases. At the same time, the structural-phase composition consists of a pseudo-pearlitic structure (ferrite-nitride mixture) and austenitic structure in different ratios since an increase in the carbon content leads to an increase in the amount of the pseudo-pearlite. The heat treatment of specimens with the mass fraction of carbon of 0.09% and 0.30% at 1250 °C for two hours leads to their complete austenization. In this case, the hardness of steels of both compositions decreases to 22 – 24 HRC (0.09 wt.% of carbon) and to 28 – 30 HRC (0.30 wt.% of carbon).

The properties of Cr,Mg-codoped bismuth tantalate pyrochlore have been investigated

Experimental refinement of monophase state regions on the phase diagrams parts of FePt and CoPt alloys

Microstructure of HIP superalloy and after subsequent hot deformation.

HPT at 6 GPa pressure in the range of 0-10 rotations of pre-quenched ingot of the commercial aluminum alloy 1965 resulted in consequential transformation of well-defined dense dislocation wall/cell structure to non-equilibrium nanofragmented one and near two-fold hardenning. The alloy strengthening and/or softening during further natural aging up to 500 hrs were within 10-15% and controlled by simultaneous decomposition of the aluminum solid solution and recovery of its deformation structure.

The process of superplastic forming into a cylindrical matrix of workpieces from the EK61 superalloy with an ultrafine-grained structure has been studied.

Structures of a thin-film high-entropy alloy deposited on steel AISI 321.

Low-heat input friction stir welding/processing of Cu-Cr-Zr alloy produces an ultrafine-grained structure reinforced with Cr and Cu5Zr nanoparticles, resulting in a hardness level of 150-190 HV1.

A ceramic material based on rare-earth zirconates with a pyrochloric structure, possessing phase and structural stability at 1300 °C was obtained. The use of REE oxide concentrate is promising for TBCs with thermal stability above 1200°C.

A cubic perovskite of complex composition Pb1/3Na1/3K1/3Ta2/3Fe1/3O3-δ (sp. gr. Pm-3m, a = 3.9767(3) Å) was synthesized for the first time by the solid-phase reaction method.

Schematic representation of distribution of microhardness over the sample cross section depending on the annealing temperature.

The features and fracture mechanisms of reactor low-activation ferritic-martensitic steel EK-181 after high-temperature thermomechanical treatment and traditional heat treatment are revealed depending on the impact test temperature in the range from -186 to 100°C. The fracture appearance transition temperature is determined by a fractographic investigation.

The influence of warm plastic deformation by rolling at 600 and 900 °C with a total strain of e = 2 on the microstructure and mechanical properties of the reactor austenitic steel EK-164 has been studied. The resulting fragmented banded microstructure with a well-developed substructure and fine grains provides high strength properties.

A new low-activation chromium-manganese austenitic steel for nuclear power engineering with an increased manganese content and additional alloying with strong carbide formers has been fabricated. The new steel has improved strength and ductility properties compared to known analogues.

The single-step (low-temperature) homogenization of the Al alloy 1570C, recommended by the alloy developers, did not lead to the complete removal of chemical heterogeneity arising during crystallization. An additional high-temperature annealing step resulted in some reduction in the alloy strength, but was effective in eliminating the chemical heterogeneity of the cast structure and increasing corrosion resistance while maintaining the grain size and dispersity and coherency of the nanosized Al3(Sc,Zr) dispersoids present in the alloy.

Better formability of the novel alloy is mainly due to the high content of the beta phase. Superplastic forming results in improvement of the microstructure homogeneity.

We observed the ordered phase particle experimentally by the TEM method. The temperature of the order–disorder phase transition in the Cu-5.9Pd alloy was estimated as Tc ≈ 340°С.

Thermal conductivity of diamond materials in transition from monocrystals to nanostructured nanodiamond composites declines two orders down due to the change in dominating factor that contributes to the thermal resistance – phonon scattering upon inner defects is changed by domination of phonon scattering at boundaries.

HAADF image of the cross section of the NiCrBSiC coating

XRD patterns from annealed Cu-Al-Cu samples after conventional (left pattern) and accumulative (right pattern) HPT.

SEM images of the graphene nanofilm in the matrix of AlMgGr composite and after it dissolution in 20% HCl. Raman spectrums of the graphene nanofilms in AlMgGr composite and the graphene films obtained after dissolution of the composite in 20% HCl.

Friction stir processing mode (ω = 2000 rpm, ν = 8 mm/min) and hardening T6 heat treatment were developed, which makes it possible to achieve the formation of a monolithic defect-free structure in the AK12D (Al–12.8Si–1.67Cu–1.03Ni–0.84Mg–0.33Mn–0.23Co–0.24Fe) alloy with a high level of mechanical properties.

General view of the equivalent strain distribution diagrams in the sample during MIF at three steps at 950, 900 and 850°C.

The mechanism of formation of the cellular crystallization structure consists in the occurrence of combined thermocapillary, concentration-capillary, evaporative-capillary and thermoelectric instability

The energy dispersive analysis showed an increase in the chromium concentration in the coating with an increase in the chromium oxide content in the electrode materials. With an increase in the concentration of Cr2O3 in the coatings, the friction coefficient and wear rate were decreased.

Terbium oxide nanopowder with an average particle size of 13 nm and a record high content of magnetoactive Tb3+ ions was successfully synthesized for the first time by laser ablation of solid target in Ar gas flow

The structure of a sample obtained by consolidation of four sheets of CP Ti was examined. It was shown that the quality of bonding between the sheets decreases from the bottom to the top and the formation of a joint of satisfactory quality was accompanied by a change in the microtexture, weak grain growth and the formation of a subgrain structure.

Theoretical model of a spherical pore in a decahedral small particle.

XRD and SEM results of the fracture of the resulting hollow rod.

CrxAl(Si)yC with a thickness of 3800 nm was deposited by PVD technique Al is chemical bonded with silicon, Si – with carbon and aluminum. Melting and crystallization of Al-Si system reduce the coating protective properties

Friction stir welding of thin aluminum and copper plates produced a welded joint in which a composite-like structure is formed.

Grain growth during recrystallization of pure iron with a submicrocrystalline structure formed by high-pressure torsion deformation at cryogenic temperature

(a) Scheme of an arbitrary pole of the sample surface (the edge of every round disc is made up of atoms at the step edges and atoms at the edge): A, C – atoms in the step edge; B – atom in the center of the plane (half of atoms bonds are broken); D – separately placed atom at the edge of the plane (has one non broken bond). (b) Field ion image of the disordered state of the alloy Fe25Pd50Au25. The statistical arrangement of atoms in the crystal lattice shows a chaotic contrast of the surface image. (c) Field ion image of the ordered state of Fe25Pd50Au25 alloy. Fe and Au atoms provide contrast in the field ion image, Pd atoms do not provide contrast.

Experimental thermogram of differential scanning calorimetry of pure polypropylene

Microstructure and crystallographic texture evolution at SCC.

Информативный рисунок показывает аномальную зависимость пиковой деформации от скорости деформации в интервале 1-100 с-1. Приведенные структуры согласуется с особенностями диаграмм нагружения.

LPBF of multiple sieved powder of Co-28 wt.% Cr-6 wt.% Mo leads to the formation of samples with inclusions of Cr and Mo within the bulk. Increasing the duration of annealing post-treatment leads to the initiation of diffusion processes, which, in its turn, leads to the gradual dissolution of Cr and Mo inclusiuons

Superplastic forming of Ti-6Al-4V commercial sheet with non-homogeneous initial microstructure (d=0.3-25 micrometers) at rather low temperature of 700C with a constant argon gas pressure of 2.5 MPa was performed for the first time. Superplastic forming of Ti-6Al-4V sheet at 700C led to an improvement of microstructure homogeneity and randomization of the rolling texture.

Танталосодержащее покрытие со сверхтвердыми включениями

Cтепень тетрагональности γ–фазы и отношение параметров решетки α2–фазы, полученные для исследуемых сплавов в дуплексных состояниях

В работе исследовано влияние длительной эксплуатации при температуре 515 °С на структуру и свойства стали марки 08Х16Н11М3. Установлено, что в процессе эксплуатации при температуре 515 °С продолжительностью 195 000 ч в стали марки 08Х16Н11М3 происходит изменение структуры с образованием вторичных фаз, инициированное выделением элементов с ограниченной растворимостью из пересыщенного твердого раствора. Изменение фазового состава в процессе теплового старения приводит к охрупчиванию стали – снижению пластичности.

Поверхность излома Al-Mg гибридов, полученных кручением под высоким давлением и последующего отжига при 275 °C

В настоящем исследовании криопрокатанный и естественно состаренный лист из сплава AA2024 и отожженные листы из технически чистого титана подвергались УЗС. Исследованы микроструктура и свойства сварных соединений после естественного старения.

Установлено, что электроимпульсная обработка криокатаной меди М1 ведет к развитию процессов возврата и непрерывной статической рекристаллизации, обеспечивает переход от рекристаллизации in-situ к росту зерен, что приводит к резкому снижению твердости.

Композитные материалы состава полиэтилен-графит-манганит проявляют положительную или отрицательную магниторезистивность в зависимости от соотношения компонентов.

Зависимость вибрационного отклика проводника на действие электрического импульса как интерференция затухающих колебаний величины ускорения, генерируемых на переднем и заднем фронтах электрического импульса при изменении длительности Timp электрического импульса.

The tensile specimen deformed by tension until fracture, the drawing of longitudinal section of the specimen and the EBSD map of the area adjacent to the fracture surface

В микроструктуре композитов на основе ZrO2 наблюдаются как неразделенные, запутанные пучки/агрегаты ОУНТ, так и отдельные нанотрубки, которые вместе образуют непрерывную армирующую структуру, что приводит к измельчению размера зерна композитов.

Фазовая трансформация типа t → m определяет неупругую стадию деформации керамики на основе диоксида циркония, стабилизированного добавками оксида иттрия. Максимум силы прогиба консолей двухконсольного образца с шевронным надрезом, испытанного расклиниванием, определяет критические характеристики трещиностойкости керамики ZrO2 + 3mol%Y2O3: скорости высвобождения энергии Gc при распространении трещины (удельной энергии разрушения) и коэффициента интенсивности напряжений KIc. Максимальная вязкость характерна для керамики состава ZrO2 + 3mol%Y2O3, отклонение от которого уменьшает показатели трещиностойкости. Повышению трещиностойкости благоприятствует измельчение порошка на планетарной мельнице.