Excess Free Volume of High Angle Grain Boundaries in Aluminium

2006 ◽  
Vol 519-521 ◽  
pp. 1557-1562 ◽  
Author(s):  
V.A. Ivanov ◽  
Dmitri A. Molodov ◽  
Lasar S. Shvindlerman ◽  
Günter Gottstein ◽  
D. Kolesnikov ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Free Volume ◽  
Pressure Range ◽  
Boundary Energy ◽  
Tilt Boundary ◽  
Triple Junctions ◽  
High Angle ◽  
Absolute Value ◽  
Excess Free Volume ◽  
Tilt Boundaries

A new method is introduced to determine the absolute value of the boundary excess free volume. Along with the boundary energy the excess free volume belongs to the major thermodynamic properties of grain boundaries. The method utilizes the dependence of the contact angle at triple junctions of grain boundaries in Al-tricrystals on hydrostatic pressure. We investigated <111> tilt boundaries in the pressure range up to 14 kbar. In particular, for a 40° <111> tilt boundary with 2° twist component the boundary free volume was found to be equal to 5.03×10-11 m3/m2.

scholarly journals The formation of excess free volume in triple junctions of and tilt boundaries in Ni at crystallization

2016 ◽  
Author(s):  
Gennady Poletaev ◽  
Darya Novoselova ◽  
Valentina Kaygorodova ◽  
Mikhail Starostenkov
Keyword(s):  
Free Volume ◽  
Triple Junctions ◽  
Excess Free Volume ◽  
Tilt Boundaries

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

2016 ◽  
Vol 247 ◽  
pp. 3-8 ◽  
Author(s):  
Gennady M. Poletaev ◽  
Darya V. Novoselova ◽  
Valentina M. Kaygorodova
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundaries ◽  
Free Volume ◽  
Crystallization Process ◽  
Triple Junctions ◽  
Phase Density ◽  
Fcc Metals ◽  
Excess Free Volume ◽  
Method Of Molecular Dynamics ◽  
Formation Conditions

The formation conditions of strained (non-equilibrium) triple junctions of grain boundaries were studied by the method of molecular dynamics. It is shown that strained triple junctions, containing excess free volume, mainly forms during crystallization process in the result of "locking" of the liquid phase density at a meeting of the three crystallization fronts and, as a consequence, of the concentration of excess free volume in the triple junction after solidification.

Grain Boundary Structure and Its Energy of Symmetric Tilt Boundary in Copper

2004 ◽  
Vol 467-470 ◽  
pp. 807-812 ◽  
Author(s):  
Naoki Takata ◽  
Kenichi Ikeda ◽  
Fusahito Yoshida ◽  
H. Nakashima ◽  
Hiroshi Abe
Keyword(s):  
Grain Boundary ◽  
Free Volume ◽  
Atomic Structure ◽  
Boundary Energy ◽  
Tilt Boundary ◽  
Grain Boundary Energy ◽  
Structural Units ◽  
Symmetric Tilt ◽  
Tilt Boundaries ◽  
Symmetric Tilt Boundary

In the present study, grain boundary energy and atomic structure of <110> symmetric tilt boundaries in copper were evaluated by molecular dynamics (MD) simulation. From the simulations, the grain boundary energy of <110> symmetric tilt boundaries depended on misorientation angle and there were large energy cusps at the misorientation angles which corresponded to (111) S 3 and (113) S 11 symmetric tilt boundaries. It was found that the atomic structure of each <110> symmetric tilt boundary was described by the combination of three kinds of structural units which consisted of (331) S 19, (111) S 3 and (113) S 11 symmetric tilt boundaries and two single crystal units which consisted of (110) S 1and (001) S 1 single crystals. From the the analysis of the excess free volume in each grain boundary, it was found that the energy of structural units depended on the excess free volume of the units and that the misorientation dependence of grain boundary energy agreed with that of the free volume in grain boundaries.

scholarly journals Исследование формирования избыточного свободного объема в тройных стыках границ зерен при кристаллизации на примере никеля

2018 ◽  
Vol 60 (5) ◽  
pp. 846
Author(s):  
Г.М. Полетаев ◽  
Д.В. Новоселова ◽  
И.В. Зоря ◽  
М.Д. Старостенков
Keyword(s):  
Molecular Dynamics ◽  
Liquid Phase ◽  
Free Volume ◽  
Triple Junctions ◽  
Phase Volume ◽  
Extended State ◽  
Dynamics Model ◽  
Excess Free Volume ◽  
High Fraction

AbstractThe formation of an excess free volume in triple junctions during crystallization has been studied by the molecular dynamics model using nickel as an example. It is shown that an excess free volume that forms during nickel crystallization in triple junctions predominantly forms as a result of the fixation of the liquid phase volume when contacting three crystallization fronts that contains, after crystallization, a high fraction of the free volume. In some cases, as the free volume is concentrated in triple junctions, a comparatively small crystalline subgrain (from one to several nanometers in diameter) forms, and the subgrain has the orientation different from those of contacting grains and exists in the extended state.

scholarly journals Молекулярно-динамическое исследование влияния концентрации вакансий на скорость миграции границ наклона в никеле

2021 ◽  
Vol 63 (5) ◽  
pp. 582
Author(s):  
Г.М. Полетаев ◽  
Р.Ю. Ракитин
Keyword(s):  
Free Volume ◽  
Driving Force ◽  
Migration Rate ◽  
Vacancy Concentration ◽  
High Angle ◽  
Vacancy Clusters ◽  
Method Of Molecular Dynamics ◽  
Initial Stage ◽  
Tilt Boundaries ◽  
Mobile Vacancy

The influence of vacancy concentration on the migration rate of high-angle tilt boundaries with misorientation axes <111> and <100> in nickel was studied by the method of molecular dynamics. It is shown that the dependence of the migration rate on the concentration of vacancies introduced at the initial stage of modeling has a maximum near 1%. The decrease in the migration rate with a further increase in the free volume is mainly due to the deceleration of the boundary by low-mobile vacancy clusters, which at high vacancy concentrations the boundary is no longer capable of sorbing. The second reason for the decrease in the migration rate with an increase in the concentration of vacancies above 1% is a decrease in the surface tension of grain boundaries and, accordingly, the driving force of their migration due to the finite sorption capacity of the boundaries with respect to the excess free volume.

Novel Approaches to the Thermodynamis of Grain Boundaries and Grain Boundary Junctions

2007 ◽  
Vol 558-559 ◽  
pp. 675-682 ◽  
Author(s):  
Lasar S. Shvindlerman ◽  
Günter Gottstein
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Free Volume ◽  
Triple Line ◽  
Line Tension ◽  
Special Technique ◽  
Line Energy ◽  
Excess Free Volume ◽  
Boundary Triple

Three recent investigations in the field of thermodynamics of grain boundaries and grain boundary junctions are presented. 1. The grain boundary excess free volume (BFV) along with the surface tension belongs to the major thermodynamic properties of grain boundaries. A special technique, recently developed, makes it possible to measure the BFV for practically any grain boundary and provides a way of estimating the grain boundary excess free volume for grain boundaries of different classes with rather high accuracy. The experimental values of the BFV measured for different grain boundaries are compared and discussed. 2. A new approach will be presented that makes it possible to correctly measure the grain boundary triple line tension. For this the topography at an equilibrated triple junction was measured by atomic force microscopy. Preliminary results of grain boundary triple line energy measurements are presented. 3. The problem is discussed whether it is possible to achieve an equilibrium grain size during grain growth in single phase alloys. Various approaches to the problem are considered. It is shown that the most realistic possibility to stabilize the grain size in a polycrystal is by impurities with negative grain boundary adsorption.

A Predictive Framework for Dislocation-Density Pile-Ups in Crystalline Systems With Coincident Site Lattice and Random Grain Boundaries

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
David M. Bond ◽  
Mohammed A. Zikry
Keyword(s):  
Dislocation Density ◽  
Grain Boundaries ◽  
Coincident Site Lattice ◽  
Local Stress ◽  
Face Centered Cubic ◽  
Slip Systems ◽  
Triple Junctions ◽  
High Angle ◽  
Site Lattice ◽  
Wide Range

Evolving dislocation-density pile-ups at grain-boundaries (GBs) spanning a wide range of coincident site lattice (CSL) and random GB misorientations in face-centered cubic (fcc) bicrystals and polycrystalline aggregates has been investigated. A dislocation-density GB interaction scheme coupled to a dislocation-density-based crystalline plasticity formulation was used in a nonlinear finite element (FE) framework to understand how different GB orientations and GB-dislocation-density interactions affect local and overall behavior. An effective Burger's vector of residual dislocations was obtained for fcc bicrystals and compared with molecular dynamics (MDs) predictions of static GB energy, as well as dislocation-density transmission at GB interfaces. Dislocation-density pile-ups and accumulations of residual dislocations at GBs and triple junctions (TJs) were analyzed for a polycrystalline copper aggregate with Σ1, Σ3, Σ7, Σ13, and Σ21 CSLs and random high-angle GBs to understand and predict the effects of GB misorientation on pile-up formation and evolution. The predictions indicate that dislocation-density pile-ups occur at GBs with significantly misoriented slip systems and large residual Burger's vectors, such as Σ7, Σ13, and Σ21 CSLs and random high-angle GBs, and this resulted in heterogeneous inelastic deformations across the GB and local stress accumulations. GBs with low misorientations of slip systems had high transmission, no dislocation-density pile-ups, and lower stresses than the high-angle GBs. This investigation provides a fundamental understanding of how different representative GB orientations affect GB behavior, slip transmission, and dislocation-density pile-ups at a relevant microstructural scale.

Structural Dependence of Grain Boundary Energy in Fe-Based Polycrystals Identified by OIM Measurements

2007 ◽  
Vol 550 ◽  
pp. 411-416
Author(s):  
Patricia Gobernado ◽  
Leo Kestens
Keyword(s):  
Grain Boundary ◽  
Boundary Energy ◽  
Initial Boundary ◽  
Geometrical Configuration ◽  
Grain Boundary Energy ◽  
Triple Junctions ◽  
High Angle ◽  
Orientation Contrast ◽  
Contrast Microscopy ◽  
Two Parameter

The (relative) grain boundary energy of random high angle boundaries has been measured in several Fe-based polycrystals. Crystallographic data obtained by orientation contrast microscopy (OIM) are combined with the geometrical configuration of grain boundaries at triple junctions. A two-parameter representation of the relative grain boundary energy in terms of misorientation angle and misorientation axis is presented. In the applied procedure a variation of the energy values assigned to one boundary was observed depending on the triangulation path chosen by the operator to connect the arbitrary initial boundary with the boundary under consideration. Results show no evidence of correspondence between the observed energy cusps and the presence of CSL boundaries.

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