Edge dislocations in fcc metals: Microscopic calculations of core structure and positron states in Al and Cu

Using nanoscale atomistic simulations it has been possible to address the problem of cross slip of a dissociated screw dislocation in an fcc metal ͑Cu͒ by a method not suffering from the limitations imposed by elasticity theory. The focus has been on different dislocation configurations relevant for cross slip via the Friedel-Escaig ͑FE͒ cross-slip mechanism. The stress free cross-slip activation energy and activation length for this mechanism are determined. We show that the two constrictions necessary for cross slip in the FE cross-slip mechanism are not equivalent and that a dislocation configuration with just one of these constrictions is energetically favored over two parallel Shockley partials. The effect of having the dislocation perpendicular to a free surface is investigated. The results are in qualitative agreement with transmission electron microscopy experiments and predictions from linear elasticity theory showing recombination or repulsion of the partials near the free surface. Such recombination at the free surface might be important in the context of cross slip because it allows the creation of the above-mentioned energetically favorable constriction alone. In addition we observe a strong preference for the partials to be in a glide plane parallel to the surface step. We have performed simulations of two screw dislocations of opposite signs, one simulation showing surface nucleated cross slip leading to subsequent annihilation of the two dislocations. It was possible to monitor the annihilation process, thereby determining the detailed dislocation reactions during annihilation. ͓S0163-1829͑97͒06630-7͔

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“…This smearing is also observed in computer simulations [34][35][36] of edge dislocations in Cu. In Fig.…”

Section: Splitting Widthsupporting

confidence: 70%

Simulations of the atomic structure, energetics, and cross slip of screw dislocations in copper

et al. 1997

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“…This is in disagreement with first results obtained with pair potentials [8,11] but confirms most recent studies using most reliable empirical potentials like EAM [17], TB-SMA [18], or pseudopotentials [15,16]. The corresponding interaction energies are displayed in Tab.…”

Section: Vacancy-dislocation Interactioncontrasting

confidence: 55%

“…On the other hand, EAM and TB-SMA potentials do not suffer such restrictions and have been shown to be well suited to study dislocation behavior. Some authors used these potentials to study the behavior of vacancies in the vicinity of dislocations, in particular to simulate pipe-diffusion in fcc metals [15][16][17][18][19][20]. These studies showed that the most stable position of the vacancy lies at the edge of the supplementary half plane corresponding to a partial dislocation and that diffusion is faster along dislocations than in the bulk.…”

Section: Introductionmentioning

confidence: 99%

The vacancy–edge dislocation interaction in fcc metals: A comparison between atomic simulations and elasticity theory

Clouet

2006

Acta Materialia

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The interaction between vacancies and edge dislocations in face centered cubic metals (Al, Au, Cu, Ni) is studied at different length scales. Using empirical potentials and static relaxation, atomic simulations give us a precise description of this interaction, mostly in the case when the separation distance between both defects is small. At larger distances, elasticity theory can be used to predict this interaction. From the comparison between both approaches we obtain the minimal separation distance where elasticity applies and we estimate the degree of refinement required in the calculation. In this purpose, isotropic and anisotropic elasticity is used assuming a perfect or a dissociated edge dislocation and considering the size effect as well as the inhomogeneity interaction.

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“…Following the conjugate-gradient relaxation, the edge dislocation splits into two partials with a stacking fault region between them. The width of stacking fault was 3.3 nm, which is within the reported values of 2.7 nm-3.6 nm for Cu [56] . This width is determined by the balance between the repulsive force of partial dislocations and the stacking fault energy.…”

Section: Simulations At the Atomic Scalesupporting

confidence: 65%

Multiscale modeling of plasticity in a copper single crystal deformed at high strain rates

Chandra

Samal

Chavan

et al. 2015

Plasticity and Mechanics of Defects

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A hierarchical multiscale modeling approach is presented to predict the mechanical response of dynamically deformed (1100 s −1 −4500 s −1 ) copper single crystal in two different crystallographic orientations. An attempt has been made to bridge the gap between nano-, micro-and meso-scales. In view of this, Molecular Dynamics (MD) simulations at nanoscale are performed to quantify the drag coefficient for dislocations which has been exploited in Dislocation Dynamics (DD) regime at the microscale. Discrete dislocation dynamics simulations are then performed to calculate the hardening parameters required by the physics based Crystal Plasticity (CP) model at the mesoscale. The crystal plasticity model employed is based on thermally activated theory for plastic flow. Crystal plasticity simulations are performed to quantify the mechanical response of the copper single crystal in terms of stressstrain curves and shape changes under dynamic loading. The deformation response obtained from CP simulations is in good agreement with the experimental data.

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Edge dislocations in fcc metals: Microscopic calculations of core structure and positron states in Al and Cu

Cited by 125 publications

References 50 publications

Simulations of the atomic structure, energetics, and cross slip of screw dislocations in copper

Simulations of the atomic structure, energetics, and cross slip of screw dislocations in copper

The vacancy–edge dislocation interaction in fcc metals: A comparison between atomic simulations and elasticity theory

Multiscale modeling of plasticity in a copper single crystal deformed at high strain rates

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