Importance of correlation effects in hcp iron revealed by a pressure-induced electronic topological transition

We discover that hcp phases of Fe and Fe0.9Ni0.1 undergo an electronic topological transition at pressures of about 40 GPa. This topological change of the Fermi surface manifests itself through anomalous behavior of the Debye sound velocity, c/a lattice parameter ratio and M\"ossbauer center shift observed in our experiments. First-principles simulations within the dynamic mean field approach demonstrate that the transition is induced by many-electron effects. It is absent in one-electron calculations and represents a clear signature of correlation effects in hcp Fe

Structural and Phase Transformations in Ti–15Mo Alloy under Thermal Influence

В работе методами оптической металлографии, РЭМ, ПЭМ, РСФА, дюрометрии проанализированы структурные и фазовые превращения в сплаве типа Ti–15Mo, протекающие при закалке из b‑области, а также при последующем старении. Установлены температурные интервалы выделения вторых фаз, их морфология и влияние на свойства (твердость).The structural and phase transformations in an alloy of the Ti–15Mo type occurring during quenching from the b-region, as well as during subsequent aging are analyzed by methods of optical metallography, SEM, TEM, RSFA and durometry. The temperature intervals of the separation of the second phases, their morphology and their influence on the properties (hardness) are established

Effect of Heat Treatment on the Structure and Properties of Steel 20H13

Samples of 20X13 steel after quenching and tempering were studied. The influence of temperature and tempering time on the structure and properties of the steel under study was estimated. The relief of fracture surface of samples after tensile tests was studied by micro-and macroanalysis.В работе изучены образцы стали 20Х13 после закалки и отпуска. Оценено влияние температуры и продолжительности отпуска на структуру и свойства исследуемой стали. Методом микро- и макроанализа исследован рельеф поверхности разрушения образцов после растяжения

STUDY OF THE INFLUENCE OF HEAT TREATMENT ON THE MECHANISMS OF FORMATION OF THE PHASE TI3AL

В работе исследовано влияние режимов термической обработки на процессы образования упорядоченной фазы Ti3Al (α2-фазы) в сплаве системы Ti–Al. Установлено, что в сплаве Ti–17Al происходит образование дисперсных частиц α2-фазы по механизму зарождения и роста.The work investigated the influence of heat treatment on the formation of ordered phase Ti3Al (α2-phase) in the alloy Ti–Al system. Established that in the alloy Ti–17Al the formation of dispersed particles of α2-phase is caused by the mechanism of nucleation and growth.Работа выполнена при поддержке гранта Президента Российской Федерации МК-7923.2016.8

Hyperspectral μ-XANES mapping in the diamond-anvil cell: analytical procedure applied to the decomposition of (Mg,Fe)-ringwoodite at the upper/lower mantle boundary

International audienceWe propose a new analytical approach to extract information from μ-X-ray Absorption Spectroscopy (XAS) based mapping techniques, where each pixel of a map contains full XANES (X-ray Absorption Near Edge Structure) information. Data reduction is performed thanks to specifically developed software, XASMAP, which allows automatic normalization, linear combination fits, map reconstruction and spectrum extraction. We illustrate an example of application on data acquired in a laser heated diamond-anvil cell, devoted to the investigation of the behavior of iron during the decomposition of (Mg,Fe)-ringwoodite into perovskite and ferropericlase at conditions relevant to Earth upper/lower mantle boundary. The analysis of 1600 Fe K-edge XANES spectra allows the reconstruction of maps based on iron-speciation, but it also drives to iron-concentration maps in a complex mixture of three crystalline phases. This analytical procedure opens the way to in situ studies at extreme conditions of pressure and temperature for the geosciences, physics and chemistry communities