V G Gavriljuk - Academia.edu (original) (raw)
Papers by V G Gavriljuk
Materials Letters, 2019
The hydrogen-caused change in the electron structure of the a-iron has been studied using the fir... more The hydrogen-caused change in the electron structure of the a-iron has been studied using the firstprinciples atomic calculations. It is shown that hydrogen entry into the a-iron crystal lattice increases the density of electron states at the Fermi level, which suggests the increase in the concentration of free electrons. The studied spatial distribution of electron density gives the evidence for corresponding enhancement of the metallic character of interatomic bonds. A strong affinity of hydrogen atoms to the grain boundaries allows to suggest a non-trivial change in their mobility.
Scripta Metallurgica et Materialia, 1992
Materials Science and Engineering: A, 2006
The effects of C, N and H in the iron-based alloys are studied in terms of the electronic and cry... more The effects of C, N and H in the iron-based alloys are studied in terms of the electronic and crystal structure, atomic distribution, phase transformations, crystal lattice defects and some peculiarities of mechanical behavior. Similarities and differences in thermodynamic behavior, structure and properties are derived from the theoretical and experimental findings showing that carbon assists the covalent character of interatomic bonds, whereas nitrogen and hydrogen increase the concentration of conduction electrons.
Exploratory Materials Science Research, 2020
METALLOFIZIKA I NOVEISHIE TEKHNOLOGII
The hydrogen and nitrogen effects on fatigue life of austenitic steels are discussed using the ab... more The hydrogen and nitrogen effects on fatigue life of austenitic steels are discussed using the ab initio calculations of electron structure, analysis of atomic distribution and dislocation substructure. As shown, both elements increase the concentration of free electrons in the f.c.c. iron softening thereby the crystal lattice, decreasing specific energy of dislocations and increasing their mobility. As a result, the dominant occurrence of short-range atomic order in the metal solid solutions causes localization of plastic deformation and consequent formation of dislocation slip bands. A combination of these factors realizes in the localized reversible planar slip of dislocations, which prevents their intersection with nucleation of submicrocracks and decreases the crack growth rate during fatigue tests, i.e., prolongs the fatigue life.
Hydrogen in Engineering Metallic Materials
The use of general descriptive names, registered names, trademarks, service marks, etc. in this p... more The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.
METALLOFIZIKA I NOVEISHIE TEKHNOLOGII
Based on the difference in diffusion mechanisms of substitutional and interstitial atoms and usin... more Based on the difference in diffusion mechanisms of substitutional and interstitial atoms and using molecular dynamics simulation of hydrogen migration, it is shown that accelerated hydrogen flux in the polycrystalline iron observed during cathodic charging cannot originate from the enhanced hydrogen grain-boundary diffusion. A possible role of grain-boundary cracking is supposed.
International Journal of Hydrogen Energy, 2017
METALLOFIZIKA I NOVEISHIE TEKHNOLOGII, 2019
Mobility of hydrogen atoms in the β-phase of titanium alloys doped with iron is studied by means ... more Mobility of hydrogen atoms in the β-phase of titanium alloys doped with iron is studied by means of mechanical spectroscopy. As shown, the hydrogen dissolution in the β-phase results in appearance of the Snoek-like relaxation at temperatures about 80 K. The ab initio atomic calculations are used to analyse atomic complexes responsible for the relaxation. The results suggest an affinity of hydrogen atom to iron in titanium and a responsible of s-H complexes (s-substitutional atom) with the symmetry lower than the cubic one for Snoek-like relaxation. The obtained activation energy of hydrogen migration in the β-phase assumes that such phase could serve as a pathway of hydrogen to the α-phase where the hydride could form.
Scripta Materialia, 2017
Comments to the paper "in situ observations of silver-decoration evolution under hydrogen permeat... more Comments to the paper "in situ observations of silver-decoration evolution under hydrogen permeation: Effects of grain boundary misorientation on hydrogen flux in pure iron", the authors: M.
Hyperfine Interactions, 2016
The role of iron in formation of the coal methane is clarified based on the studies performed on ... more The role of iron in formation of the coal methane is clarified based on the studies performed on the coal samples taken from different mines in Donetsk coal basin. Using Mössbauer spectroscopy, a correlation is found between the iron content and methane capacity of coal seams. By means of electron paramagnetic resonance, it is found that iron increases the concentration of non-compensated electron spins, i.e. dangled bonds at the carbon atoms. These bonds can be occupied by hydrogen atoms as a prerequisite of methane formation. The two-valence iron is shown to be the most effective in the increase of spin concentration. By using the ion mass spectrometry, the modelling of methane formation is carried out on the mechanical mixture of the iron-free reactor graphite, iron compounds and diluted sulphuric acid as a source of hydrogen atoms. The proposed mechanism is also confirmed by methane formation in the mixture of iron compounds and the coal from the mine where the iron and methane are practically absent.
International Journal of Hydrogen Energy, 2017
CrNi austenitic steels and titanium alloy Ti-10V-2Fe-3Al are studied aiming to clarify a reason f... more CrNi austenitic steels and titanium alloy Ti-10V-2Fe-3Al are studied aiming to clarify a reason for difference between two classes of engineering materials in their sensitivity to hydrogen brittleness. Using ab initio calculations, it is found that hydrogen increases density of electron states at the Fermi level in both materials except for its decrease in the titanium alloy at extremely high hydrogen contents. Migration of hydrogen atoms and their interaction with dislocations are studied using mechanical spectroscopy. The enthalpies of hydrogen atoms migration and their binding to dislocations, as well as temperature for condensation of hydrogen clouds around dislocations, are shown to be significantly larger in austenitic steels in comparison with the b titanium alloy. This is a reason for lower temperature range of hydrogen embrittlement in the titanium alloys. The different hydrogen effect in the studied materials and usage of hydrogen as temporary alloying element increasing plasticity of titanium alloys in the course of their processing are interpreted within the frame of HELP theory.
Materials Science Forum, 2007
Three main hypotheses of hydrogen embrittlement (HE) of austenitic steels are discussed based on ... more Three main hypotheses of hydrogen embrittlement (HE) of austenitic steels are discussed based on the studies of the interatomic interactions, hydrogen-induced phase transformations and dislocations properties. Measurements of electron spin resonance and ab initio calculations of the electron structure witness that the concentration of conduction electrons increases due to hydrogen, which enhances the metallic character of interatomic bonds. The hypothesis of brittle hydrogen-induced phases is disproved by the studies of the silicon-alloyed steels: the silicon-caused increase in the fraction of the εH martensite is accompanied by the decrease of HE. Studies of strain-dependent internal friction have shown the hydrogen-caused decrease in the start stress of microplasticity and increase in the velocity of dislocations in accordance with HELP hypothesis. A mechanism of HELP is proposed based on the hydrogencaused enhancement of the metallic character of interatomic bonds, which results ...
ISIJ International, 1996
A short review of beneficial effects of nitrogen in steel is given including mechanical and corro... more A short review of beneficial effects of nitrogen in steel is given including mechanical and corrosion properties, and the data of interatomic interactions and distribution of solute atoms in solid solutions are discussed with the aim of explanation of the physical nature of nitrogen steels. The concept is presented according to which alloying by nitrogen enhancesthe metallic component of interatomic bondsand provides more homogeneous distribution of substitutionai solutes through short range ordering of nitrogen atoms and strong chemical interaction between nitrogen and al]oying elements, which results in the high thermodynamical stability of nitrogen austenitic steeis. Theopposite tendency to clustering and concentration inhomogeneity of austenitic steels dueto carbon is shown. I nheritance of the atomic distribution by martensite is discussed in terms of short range atomic order and data on crystal structure of precipitations during tempering of nitrogen martensite are presented as comparedto carbon and carbon+nitrogen martensites KEYWORDS: nitrogen; carbon; austenite; martensite; toughness; strength; creep rate; fatigue; wear resistance; corrosion; state density on the Fermi surface; short range ordering; clustering, tempering: nitrides; carbides. 1.
Hydrogen in Engineering Metallic Materials, 2022
Materials Science Forum, 1999
ABSTRACT
METALLOFIZIKA I NOVEISHIE TEKHNOLOGII, 2016
METALLOFIZIKA I NOVEISHIE TEKHNOLOGII, 2016
Materialwissenschaft und Werkstofftechnik, 2008
... Nach Festwalzen der Oberfläche liegt eine Höchsthärte von rund 60 HRC vor Bild 3, die sich na... more ... Nach Festwalzen der Oberfläche liegt eine Höchsthärte von rund 60 HRC vor Bild 3, die sich nach Warmauslagern bei ... gehalt dazwischen, so bleibt der Zustand bis zur absoluten Temperatur nicht magnetisierbar, wobei unterhalb der Néel-Temperatur der antiferromagnetische ...
Journal of Applied Physics, 2011
Using Mössbauer spectroscopy and electron paramagnetic resonance, it is shown that Fe2+ and Fe3+ ... more Using Mössbauer spectroscopy and electron paramagnetic resonance, it is shown that Fe2+ and Fe3+ compounds in the coal increase the spin concentration in the carbon nanoclusters (aromatic area) and in the intercluster space (aliphatic medium). The Fe2+ compounds preferentially support the increase of dangled bonds in carbon nanoclusters, whereas the Fe3+ ones assist the formation of free radicals in the
Materials Letters, 2019
The hydrogen-caused change in the electron structure of the a-iron has been studied using the fir... more The hydrogen-caused change in the electron structure of the a-iron has been studied using the firstprinciples atomic calculations. It is shown that hydrogen entry into the a-iron crystal lattice increases the density of electron states at the Fermi level, which suggests the increase in the concentration of free electrons. The studied spatial distribution of electron density gives the evidence for corresponding enhancement of the metallic character of interatomic bonds. A strong affinity of hydrogen atoms to the grain boundaries allows to suggest a non-trivial change in their mobility.
Scripta Metallurgica et Materialia, 1992
Materials Science and Engineering: A, 2006
The effects of C, N and H in the iron-based alloys are studied in terms of the electronic and cry... more The effects of C, N and H in the iron-based alloys are studied in terms of the electronic and crystal structure, atomic distribution, phase transformations, crystal lattice defects and some peculiarities of mechanical behavior. Similarities and differences in thermodynamic behavior, structure and properties are derived from the theoretical and experimental findings showing that carbon assists the covalent character of interatomic bonds, whereas nitrogen and hydrogen increase the concentration of conduction electrons.
Exploratory Materials Science Research, 2020
METALLOFIZIKA I NOVEISHIE TEKHNOLOGII
The hydrogen and nitrogen effects on fatigue life of austenitic steels are discussed using the ab... more The hydrogen and nitrogen effects on fatigue life of austenitic steels are discussed using the ab initio calculations of electron structure, analysis of atomic distribution and dislocation substructure. As shown, both elements increase the concentration of free electrons in the f.c.c. iron softening thereby the crystal lattice, decreasing specific energy of dislocations and increasing their mobility. As a result, the dominant occurrence of short-range atomic order in the metal solid solutions causes localization of plastic deformation and consequent formation of dislocation slip bands. A combination of these factors realizes in the localized reversible planar slip of dislocations, which prevents their intersection with nucleation of submicrocracks and decreases the crack growth rate during fatigue tests, i.e., prolongs the fatigue life.
Hydrogen in Engineering Metallic Materials
The use of general descriptive names, registered names, trademarks, service marks, etc. in this p... more The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.
METALLOFIZIKA I NOVEISHIE TEKHNOLOGII
Based on the difference in diffusion mechanisms of substitutional and interstitial atoms and usin... more Based on the difference in diffusion mechanisms of substitutional and interstitial atoms and using molecular dynamics simulation of hydrogen migration, it is shown that accelerated hydrogen flux in the polycrystalline iron observed during cathodic charging cannot originate from the enhanced hydrogen grain-boundary diffusion. A possible role of grain-boundary cracking is supposed.
International Journal of Hydrogen Energy, 2017
METALLOFIZIKA I NOVEISHIE TEKHNOLOGII, 2019
Mobility of hydrogen atoms in the β-phase of titanium alloys doped with iron is studied by means ... more Mobility of hydrogen atoms in the β-phase of titanium alloys doped with iron is studied by means of mechanical spectroscopy. As shown, the hydrogen dissolution in the β-phase results in appearance of the Snoek-like relaxation at temperatures about 80 K. The ab initio atomic calculations are used to analyse atomic complexes responsible for the relaxation. The results suggest an affinity of hydrogen atom to iron in titanium and a responsible of s-H complexes (s-substitutional atom) with the symmetry lower than the cubic one for Snoek-like relaxation. The obtained activation energy of hydrogen migration in the β-phase assumes that such phase could serve as a pathway of hydrogen to the α-phase where the hydride could form.
Scripta Materialia, 2017
Comments to the paper "in situ observations of silver-decoration evolution under hydrogen permeat... more Comments to the paper "in situ observations of silver-decoration evolution under hydrogen permeation: Effects of grain boundary misorientation on hydrogen flux in pure iron", the authors: M.
Hyperfine Interactions, 2016
The role of iron in formation of the coal methane is clarified based on the studies performed on ... more The role of iron in formation of the coal methane is clarified based on the studies performed on the coal samples taken from different mines in Donetsk coal basin. Using Mössbauer spectroscopy, a correlation is found between the iron content and methane capacity of coal seams. By means of electron paramagnetic resonance, it is found that iron increases the concentration of non-compensated electron spins, i.e. dangled bonds at the carbon atoms. These bonds can be occupied by hydrogen atoms as a prerequisite of methane formation. The two-valence iron is shown to be the most effective in the increase of spin concentration. By using the ion mass spectrometry, the modelling of methane formation is carried out on the mechanical mixture of the iron-free reactor graphite, iron compounds and diluted sulphuric acid as a source of hydrogen atoms. The proposed mechanism is also confirmed by methane formation in the mixture of iron compounds and the coal from the mine where the iron and methane are practically absent.
International Journal of Hydrogen Energy, 2017
CrNi austenitic steels and titanium alloy Ti-10V-2Fe-3Al are studied aiming to clarify a reason f... more CrNi austenitic steels and titanium alloy Ti-10V-2Fe-3Al are studied aiming to clarify a reason for difference between two classes of engineering materials in their sensitivity to hydrogen brittleness. Using ab initio calculations, it is found that hydrogen increases density of electron states at the Fermi level in both materials except for its decrease in the titanium alloy at extremely high hydrogen contents. Migration of hydrogen atoms and their interaction with dislocations are studied using mechanical spectroscopy. The enthalpies of hydrogen atoms migration and their binding to dislocations, as well as temperature for condensation of hydrogen clouds around dislocations, are shown to be significantly larger in austenitic steels in comparison with the b titanium alloy. This is a reason for lower temperature range of hydrogen embrittlement in the titanium alloys. The different hydrogen effect in the studied materials and usage of hydrogen as temporary alloying element increasing plasticity of titanium alloys in the course of their processing are interpreted within the frame of HELP theory.
Materials Science Forum, 2007
Three main hypotheses of hydrogen embrittlement (HE) of austenitic steels are discussed based on ... more Three main hypotheses of hydrogen embrittlement (HE) of austenitic steels are discussed based on the studies of the interatomic interactions, hydrogen-induced phase transformations and dislocations properties. Measurements of electron spin resonance and ab initio calculations of the electron structure witness that the concentration of conduction electrons increases due to hydrogen, which enhances the metallic character of interatomic bonds. The hypothesis of brittle hydrogen-induced phases is disproved by the studies of the silicon-alloyed steels: the silicon-caused increase in the fraction of the εH martensite is accompanied by the decrease of HE. Studies of strain-dependent internal friction have shown the hydrogen-caused decrease in the start stress of microplasticity and increase in the velocity of dislocations in accordance with HELP hypothesis. A mechanism of HELP is proposed based on the hydrogencaused enhancement of the metallic character of interatomic bonds, which results ...
ISIJ International, 1996
A short review of beneficial effects of nitrogen in steel is given including mechanical and corro... more A short review of beneficial effects of nitrogen in steel is given including mechanical and corrosion properties, and the data of interatomic interactions and distribution of solute atoms in solid solutions are discussed with the aim of explanation of the physical nature of nitrogen steels. The concept is presented according to which alloying by nitrogen enhancesthe metallic component of interatomic bondsand provides more homogeneous distribution of substitutionai solutes through short range ordering of nitrogen atoms and strong chemical interaction between nitrogen and al]oying elements, which results in the high thermodynamical stability of nitrogen austenitic steeis. Theopposite tendency to clustering and concentration inhomogeneity of austenitic steels dueto carbon is shown. I nheritance of the atomic distribution by martensite is discussed in terms of short range atomic order and data on crystal structure of precipitations during tempering of nitrogen martensite are presented as comparedto carbon and carbon+nitrogen martensites KEYWORDS: nitrogen; carbon; austenite; martensite; toughness; strength; creep rate; fatigue; wear resistance; corrosion; state density on the Fermi surface; short range ordering; clustering, tempering: nitrides; carbides. 1.
Hydrogen in Engineering Metallic Materials, 2022
Materials Science Forum, 1999
ABSTRACT
METALLOFIZIKA I NOVEISHIE TEKHNOLOGII, 2016
METALLOFIZIKA I NOVEISHIE TEKHNOLOGII, 2016
Materialwissenschaft und Werkstofftechnik, 2008
... Nach Festwalzen der Oberfläche liegt eine Höchsthärte von rund 60 HRC vor Bild 3, die sich na... more ... Nach Festwalzen der Oberfläche liegt eine Höchsthärte von rund 60 HRC vor Bild 3, die sich nach Warmauslagern bei ... gehalt dazwischen, so bleibt der Zustand bis zur absoluten Temperatur nicht magnetisierbar, wobei unterhalb der Néel-Temperatur der antiferromagnetische ...
Journal of Applied Physics, 2011
Using Mössbauer spectroscopy and electron paramagnetic resonance, it is shown that Fe2+ and Fe3+ ... more Using Mössbauer spectroscopy and electron paramagnetic resonance, it is shown that Fe2+ and Fe3+ compounds in the coal increase the spin concentration in the carbon nanoclusters (aromatic area) and in the intercluster space (aliphatic medium). The Fe2+ compounds preferentially support the increase of dangled bonds in carbon nanoclusters, whereas the Fe3+ ones assist the formation of free radicals in the