Grain Boundary Shear Coupling is Not a Grain Boundary Property

Chen, Kongtao; Han, Jian; Thomas, Spencer L.; Srolovitz, David J.

doi:10.2139/ssrn.3289657

Cited by 3 publications

(12 citation statements)

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“…The value of β is calculated by crystallography and, by the prior determination (via atomistic simulations [24,55]) of the most likely deformation mode for the boundary. For any rational GB there is a countably infinite number of shear coupling factors, and it is possible for a boundary to move by one or more of those factors [17,45]. This model currently aims to capture one shear coupling mode only.…”

Section: Diffuse Boundary Modelmentioning

confidence: 99%

“…Boundary 1 and 2 are 0 0 1 tilt boundaries with {5 1 0} and {7 5 0} boundary planes, respectively, and Boundary 3 is a 1 1 1 tilt boundary with an {1 2 3} boundary plane. Previous work has examined these and other boundaries using both molecular dynamics [63] and a disconnection-based model for grain boundary migration [17,23,36]. Parameters for these values were determined manually and from literature (Table II).…”

Section: Gb1 Gb2 Gb3mentioning

confidence: 99%

“…Microstructure evolution is primarily mediated through the motion of grain boundaries (GBs). GB migration is a complex, non-equilibrium, dissipative process that exhibits a vast range of behaviors depending on crystallography and loading conditions, and there is still little consensus on what constitutes intrinsic GB migration properties [17]. Current knowledge of GB migration behavior has been built up predominantly through atomistic simulations [18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Multiphase field modeling of grain boundary migration mediated by emergent disconnections

Gokuli,

Runnels

2021

Preprint

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Knowledge about grain boundary migration is a prerequisite for understanding and ultimately modulating the properties of polycrystalline materials. Evidence from experiments and molecular dynamics (MD) simulations suggests that the formation and motion of disconnections is a mechanism for grain boundary migration. Here, grain boundary migration is modeled using a multiphase field model based on the principle of minimum dissipation potential with nonconvex boundary energy, along with a stochastic model for thermal nucleation of disconnection pairs. In this model, disconnections arise spontaneously in the presence of an elastic driving force, and that their motion mediates boundary migration. The effect is due to the fact that the formation of the disconnections pairs results in a stress concentration, causing the elastic driving force to exceed the threshold value and driving the propagation of the disconnection along the interface. The model is applied to study the propagation/annihilation of single disconnection pairs, the relaxation of a perturbed interface, and shear coupling at various temperatures. The results are consistent with the current understanding of disconnections, and capture the effect of thermal softening.

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Section: Diffuse Boundary Modelmentioning

confidence: 99%

Section: Gb1 Gb2 Gb3mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Multiphase field modeling of grain boundary migration mediated by emergent disconnections

Gokuli,

Runnels

2021

Preprint

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“…The disconnection character is limited by the underlying GB crystallography [3,23]. More specifically, GB bicrystallography allows for an infinite, discrete set of possible disconnection types or modes {b, H} [18]; the relative importance of these modes depends on disconnection mobilities and equilibrium disconnection densities, and may be analyzed within a statistical mechanics framework [42,5]. Many GB dynamical phenomena require consideration of multiple disconnection modes [18].…”

Section: Introductionmentioning

confidence: 99%

“…(2) The flux of disconnection Burgers vectors into a TJ from the constituent GBs generally results in Burgers vector accumulation at the TJ which generates long range stresses that affect disconnection mode selection and GB/TJ evolution. (3) The "apparent" or "effective" GB mobility is a statistical average of the properties of the multiple disconnection modes that are operative and their responses to different types of driving forces [5,50]. (4) The relation between the disconnection mechanism-based description of TJ motion and the conventional capillarity-driven model is unclear.…”

Section: Introductionmentioning

confidence: 99%

Grain boundary triple junction dynamics: a continuum disconnection model

Wei¹,

Zhang²,

Han³

et al. 2019

Preprint

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The microstructure of polycrystalline materials consists of networks of grain boundaries (GBs) and triple junctions (TJs), along which three GBs meet. The evolution of such microstructures may be driven by surface tension (capillarity), applied stresses, or other means that lead to a jump in chemical potential across the GBs. Here, we develop a model for the concurrent evolution of the GB/TJ network based upon the microscopic mechanism of motion; the motion of line defects (disconnections) in the GB that have both dislocation and step character. The evolution involves thermally-activated disconnection formation/annihilation and migration of multiple disconnections modes/types. We propose this crystallography-respecting continuum model for the disconnection mechanism of GB/TJ dynamics derived with a variational approach based on the principle of maximum energy dissipation. The resultant TJ dynamics is reduced to an optimization problem with constraints that account for local microstructure geometry, conservation of Burgers vectors, and thermal-kinetic limitations on disconnection fluxes. We present analysis of and numerical simulations based upon our model to demonstrate the dependence of the GB and TJ mobilities and the TJ drag effect on the disconnection properties, and compare the predictions with molecular dynamics and experimental observations.

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A Continuum Multi-Disconnection-Mode model for grain boundary migration

Wei¹,

Thomas²,

Han³

et al. 2019

Journal of the Mechanics and Physics of Solids

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We study the Grain Boundary (GB) migration based on the underlying disconnection structure and mechanism. Disconnections are line defects that lie solely within a GB and are characterized by both a Burgers vector and a step height, as set by the GB bicrystallography. Multiple disconnection modes can nucleate, as determined by their formation energy barriers and temperature, and move along the GB under different kinds of competing driving forces including shear stress and chemical potential jumps across the GBs. We present a continuum model in two dimensions for GB migration where the GB migrates via the thermally-activated nucleation and kinetically-driven motion of disconnections. We perform continuum numerical simulations for investigating the GB migration behavior in single and multi-mode disconnection limits in both a bicrystal (under two types of boundary conditions) and for a finite-length GB with pinned ends. The results clearly demonstrate the significance of including the coupling and competing between different disconnection modes and driving forces for describing the complex and diverse phenomena of GB migration within polycyrstalline microstructures.

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Grain Boundary Shear Coupling is Not a Grain Boundary Property

Cited by 3 publications

References 0 publications

Multiphase field modeling of grain boundary migration mediated by emergent disconnections

Multiphase field modeling of grain boundary migration mediated by emergent disconnections

Grain boundary triple junction dynamics: a continuum disconnection model

A Continuum Multi-Disconnection-Mode model for grain boundary migration

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