Atomic processes of shear-coupled migration in 
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 twins and vicinal grain boundaries in bcc-Fe

Kvashin, N.; García-Muller, Pablo; Anento, N.; Serra, A.

doi:10.1103/physrevmaterials.4.073604

Cited by 20 publications

(35 citation statements)

References 40 publications

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“…But numerous other potential disconnections (the one represented by black arrows) present in the dichromatic patterns did not activate. These latter ones may be activated by heterogeneous disconnection nucleation: vacancies [43,44], triple junctions [45], sessile disconnections [46,47] or other GB imperfections can be a source of glissile disconnections and could potentially produce disconnections that have not been observed.…”

Section: Discussionmentioning

confidence: 99%

Multiple coupling modes to relax shear strain during grain boundary migration

Combe

Mompiou²,

Legros³

2021

Acta Materialia

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Shear-coupled grain boundary (GB) migration is an effective plastic mechanism in absence of dislocation activity, ie. more favorably in nanocrystalline metals. For a given GB, several stress induced migration mechanisms, referred as coupling modes participate to the decrease of the elastic energy produced by the shear. They operate through the nucleation and motion of interfacial defects known as disconnections, carrying elementary shear strain characterized by their Burgers vector. However, so far, the coupling modes have been studied only under a simple shear, a situation much less complex than expected in a strained polycrystal, where multiple components of the stress tensor are present. Here we propose a more systematic investigation of the coupling modes when a composite shear is applied. This promotes the activation of new coupling modes. Using Molecular Dynamics simulations, we evidence these multiple coupling modes and the operation of their associate disconnections. Moreover, we also show that, even at low temperature, GB migration may occur by the successive occurrence of two modes: the relaxed shear appears then as an effective parameter, resulting from the combination of two operating elementary mechanisms.

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Section: Discussionmentioning

confidence: 99%

Multiple coupling modes to relax shear strain during grain boundary migration

Combe

Mompiou²,

Legros³

2021

Acta Materialia

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“…Like GBDs at the {112} interface, the GBDs at the {332} interface can act as a source of disconnections [31] under certain conditions, as detailed below. The evolution of the Bv of the risers depends on the number of dislocations of the pileup that are absorbed.…”

Section: {332} Gb-dislocation Reactionsmentioning

confidence: 99%

Interaction of a dislocation pileup with {332} tilt grain boundary in bcc metals studied by MD simulations

Kvashin

Anento

Terentyev

et al. 2021

Phys. Rev. Materials

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The sustainability and capacity of macroscopic deformation by polycrystalline metals and metallic alloys is controlled by the propagation of dislocation-mediated slip through grains. In this paper, the interaction of a pileup of 1 /2 111 dislocations with the {332} tilt grain boundary (GB) is studied as a function of temperature in three bcc metals: iron (Fe), chromium (Cr), and tungsten (W). The interaction results in the transformation of the crystal dislocation into GB dislocations. The {332} tilt GB absorbs the crystal dislocations of the pileup, neither the transmission nor reflection of dislocations was observed. The reaction product at the GB is determined by the crystallography of the GB and the features of the crystal dislocations involved, specifically, the orientation of the Burgers vector and the glide plane of the dislocation. In general, the decomposition results in the formation of a sessile GB dislocation with a riser that facets the GB and several elementary disconnections that glide away. In some cases, the riser increases its length with the number of dislocations absorbed and a new asymmetrical grain boundary of {112}/{110} type is created. For a given external shear stress, the number of dislocations absorbed depends on the orientation of the Burgers vector, glide plane of the pileup, and material.

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“…As with plasticity by dislocation motion, boundary motion relies on disconnection nucleation in addition to propagation. Disconnections can nucleate in many ways; grain boundary dislocations [64,65], triple junctions [66], or other interfaces [67] can act as disconnection sources. However for large, pristine boundaries, disconnection nucleation becomes primarily a thermally activated process.…”

Section: B Nucleation Modelmentioning

confidence: 99%

Multiphase field modeling of grain boundary migration mediated by emergent disconnections

Gokuli

Runnels

2021

Acta Materialia

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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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Atomic processes of shear-coupled migration in {112} twins and vicinal grain boundaries in bcc-Fe

Cited by 20 publications

References 40 publications

Multiple coupling modes to relax shear strain during grain boundary migration

Multiple coupling modes to relax shear strain during grain boundary migration

Interaction of a dislocation pileup with {332} tilt grain boundary in bcc metals studied by MD simulations

Multiphase field modeling of grain boundary migration mediated by emergent disconnections

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