The Causes of Formation of the Triple Junctions of Grain Boundaries Containing Excess Free Volume in fcc Metals at Crystallization

Полетаев, Г. М.; Novoselova, D. V.; Kaygorodova, Valentina M.

doi:10.4028/www.scientific.net/ssp.247.3

Cited by 15 publications

(11 citation statements)

References 9 publications

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“…Indeed, the evolutionary formation of grain boundary networks can be described by crystallization or defect-mediated grain boundary migration [29] with more complex crystallographic constraints at the TJ leading to well-established TJ drag [30]. And it is reasonable that both crystallization and migration can trap complex metastable defects and excess free volume in the TJ, such as illustrated in the work by Poletaev et al [31,32]. This dynamics becomes even more complex during radiation events that are can alter the shape, location, and character of grain boundaries and triple junctions [33][34][35].…”

Section: Comparison To Experimental Observations and Relevance Of Thementioning

confidence: 99%

Statistical analysis of the interaction between irradiation-induced defects and triple junctions

Zarnas

Dingreville

Muntifering

et al. 2020

Adv. Model. and Simul. in Eng. Sci.

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By using a generalized, spatially resolved rate theory, we systematically studied the irradiation-induced diffusion and segregation of point defects near triple junctions. Our model captured not only the formation, growth, and recombination of point defects but also the interaction of these defects with pre-existing defects. We coupled the stress field of the triple junction with defect diffusion via a modified chemical potential. The residual stress fields of grain boundaries and triple junctions are modeled via disclination mechanics theory. By assessing the behavior of 144 triple junctions with vacancy and interstitial defects, we correlated defect-sink efficiencies with key characteristics of triple junctions. For vacancies, the geometric configuration of triple junctions dominated sink efficiency, suggesting that equiaxed grains would resist the accumulation of vacancies more than elongated grains. For interstitials, the sink density of the grain boundaries composing the triple junctions dominated sink efficiency. Hence, the interstitial concentration may be managed by adjusting the structure of the grain boundaries. Overall, we illustrated the complex coupling between pre-existing defects and radiation-induced defects through interaction of their stress fields. This theoretical framework provides an efficient tool to rapidly assess defect management in microstructures.

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Section: Comparison To Experimental Observations and Relevance Of Thementioning

confidence: 99%

Statistical analysis of the interaction between irradiation-induced defects and triple junctions

Zarnas

Dingreville

Muntifering

et al. 2020

Adv. Model. and Simul. in Eng. Sci.

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“…2). Согласно нашим предыдущим исследованиям [13,14,24], свободный объем концентрируется в тройном стыке при затвердевании в области, имеющей радиус около 1 нм. Доля удаленных атомов из рассматриваемой области варьировалась от 0 % до 80 %.…”

Section: результаты и обсуждениеunclassified

“…Диффузия в области тройного стыка границ зерен протекает значительно интенсивнее, чем вдоль самих границ [10], его структура является сравнительно более «рыхлой» [11], иногда даже с включениями аморфной фазы [12]. В работах [13,14] с помощью компьютерного моделирования мы проанализировали различные причины формирования свободного объема в тройных стыках и пришли к выводу, что избыточный свободный объем образуется в стыках преимущественно в процессе кристаллизации в результате «запирания» плотности жидкой фазы при встрече трех фронтов кристаллизации и, как следствие, концентрирования избыточного свободного объема в тройном стыке после затвердевания.…”

Section: Introductionunclassified

Investigation of the influence of excess free volume on the mobility of triple junctions of grain boundaries

Novoselova¹,

Полетаев²,

Kovalenko³

2018

LoM

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The effect of excess free volume on the mobility of triple junctions of grain boundaries by the example of nickel was studied by the molecular dynamics method. According to experimental data, triple junctions in polycrystals in most cases contain more specific free volume compared with the grain boundaries that form these junctions. Triple junctions of tilt boundaries with <100> and <111> misorientation axes were considered. Migration of the junctions was simulated by creating a nonequilibrium configuration of the joining boundaries-their migration, as a result of which they took an equilibrium position, led to migration of the triple junction (model proposed by L. S. Shvindlerman and co-authors). The interactions of nickel atoms with each other in the molecular dynamics model were described by the many-body Cleric-Rosato potential constructed within the tight binding model. The free volume was introduced locally into the triple junction region with the radius of 1 nm. The percentage of the removed atoms from the considered region was varied from 0 % to 80 %. Molecular dynamic simulation showed that the migration velocity of the triple junction is practically independent of the free volume value. This is explained by the fact that most part of the free volume introduced at the initial stage does not migrate with the triple junction but remains at the point where it was introduced and distributed along the boundary which lengthens during the migration of the junction. The smaller part of the free volume however remains in the joint but its presence has little effect on the mobility of the triple junction. This is mainly influenced by the mobility of the joining boundaries and the ratio of their tension.

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“…Дело в том, что для формирования крис таллической структуры из жидкого состояния требуются очень малые (по меркам молекулярной динамики) скорости охлаждения -примерно 10 12 К/с. При обычных скоростях охлаждения, используемых в молекулярной динамике (10 15 - 10 16 К/с), при затвердевании из жидкого состояния образуется аморфная структура [13,14]. При создании расчетного блока цилиндрические области с кристаллической структурой поворачивали на случайные или заданные углы вокруг центральной оси цилиндров; это делали для того, чтобы конечные кристаллические зерна имели по завершении кристаллизации между собой границы наклона.…”

Section: аннотация методом молекулярной динамики проведено исследоваunclassified

Interaction of Hydrogen Impurity With Nanocrystalline Palladium and Nickel

Полетаев¹,

Зоря²,

Ракитин³

2018

Izv. vysš. učebn. zaved., Čern. metall.

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The interaction of hydrogen atoms with nanocrystalline palladium and nickel in the work was studied by the molecular dynamics method. The nanocrystalline structure of palladium and nickel was created in the model by crystallization from the liquid state at the presence of several specially introduced crystalline embryos. After solidification, the calculation blocks, in addition to the crystalline phase, contained grain boundaries and triple junctions of grain boundaries. The interactions of metal atoms with each other were described by the multi-particle Cleri-Rosato potential constructed in the framework of the tight-binding model. Morse potentials were used to describe the interactions of hydrogen atoms with metal atoms and with each other. The parameters of Morse potentials were calculated from the experimental data of theabsorption energy, the activation energy of the above-barrier diffusion of hydrogen in a metal (at normal and high temperatures), the binding energy with a vacancy, dilatation. According to the results obtained in the present work, at a high concentration of hydrogen (the concentration of 10% from the metal atoms was considered), the hydrogen atoms combine into aggregates, which are formed predominantly near the surface of the metal. The aggregates contained, as a rule, several dozen hydrogen atoms and had low diffusion activity. The binding energy of hydrogen atoms with these aggregates was greater than with the metal crystal lattice or grain boundaries in it. In palladium, hydrogen aggregates were formed farther from the surface than in nickel. Apparently, this is due not so much to the relatively low energy of hydrogen absorption by palladium (–0.1 eV) in comparison with nickel (0.16 eV), but rather to the difference in lattice parameters of the metals under consideration: 3.89 Å for Pd and 3.524 Å for Ni. For the same reason, conspicuously, hydrogen aggregates in a pure crystal lattice were more often observed in Pd than in Ni. In Ni, aggregates, as a rule, were formed in defect areas containing an excess free volume: near the free surface, in grain boundaries and in triple junctions.

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The Causes of Formation of the Triple Junctions of Grain Boundaries Containing Excess Free Volume in fcc Metals at Crystallization

Cited by 15 publications

References 9 publications

Statistical analysis of the interaction between irradiation-induced defects and triple junctions

Statistical analysis of the interaction between irradiation-induced defects and triple junctions

Investigation of the influence of excess free volume on the mobility of triple junctions of grain boundaries

Interaction of Hydrogen Impurity With Nanocrystalline Palladium and Nickel

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