Prediction of Dislocation Cores in Aluminum from Density Functional Theory

Random solid solution alloys are a broad class of materials that are used across the entire spectrum of engineering metals, whether as stand-alone materials (e.g. Al-5xxx alloys) or as the matrix in precipitatestrengthening materials (e.g. Ni-based superalloys). As a result, the mechanisms of, and prediction of, strengthening in solid solutions has a long history. Many concepts have been developed and important trends identified but predictive capability has remained elusive. In recent years, a new theory has been developed that builds on one historical model, the Labusch model, in important ways that lead to a well-defined model valid for random solutions with arbitrary numbers of components and compositions. The new theory uses first-principles-computed solute/dislocation interaction energies as input, from which specific predictions emerge for the yield strength and activation volume as a function of alloy composition, temperature, and strain-rate. Being a general model for materials that otherwise have a low Peierls stress, it has broad application and has been successfully applied to Al-X alloys, Mg-Al, twinning in Mg alloys, and recently fcc High-Entropy Alloys. Here, the new theory is presented in a general and systematic manner. Approximations and limiting cases that reduce the complexity and facilitate understanding are introduced, and help relate the new model to various physical features present among the historical array of models. The quantitative predictions of the model in the various materials above is then demonstrated.

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“…The edge dislocation core was computed by previously [80] and corresponds to the structure shown in Fig. 1a.…”

Section: Al-mn Solid Solutionsmentioning

confidence: 99%

Solute strengthening in random alloys

et al. 2017

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“…However, the number of possible stable dislocation cores and their corresponding atomicscale structures are not known in advance. A coherent strategy is therefore indispensable to combine the experimental imaging with comprehensive theoretical simulations in a self-consistent global optimization scheme 19,20 .…”

mentioning

confidence: 99%

Polymorphism of dislocation core structures at the atomic scale

et al. 2014

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Dislocation defects together with their associated strain fields and segregated impurities are of considerable significance in many areas of materials science. However, their atomic-scale structures have remained extremely challenging to resolve, limiting our understanding of these ubiquitous defects. Here, by developing a complex modelling approach in combination with bicrystal experiments and systematic atomic-resolution imaging, we are now able to pinpoint individual dislocation cores at the atomic scale, leading to the discovery that even simple magnesium oxide can exhibit polymorphism of core structures for a given dislocation species. These polymorphic cores are associated with local variations in strain fields, segregation of defects, and electronic states, adding a new dimension to understanding the properties of dislocations in real materials. The findings advance our fundamental understanding of basic behaviours of dislocations and demonstrate that quantitative prediction and characterization of dislocations in real materials is possible.

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“…The classical model from dislocation theory for stacking fault widths does not consistently fit the experimental data for all metals [9,21]. MD is the current numerical choice for core calculations; however, results are dependent on the interatomic potential used in the calculations [9,[22][23][24][25]. Figure 2a shows the relationship between w 0 , as calculated with PFDD, in relation to the normalized intrinsic SFE γ I /μb.…”

Section: Extended Dislocationsmentioning

confidence: 99%

“…The (c) 11 and (c) 22 are the in-plane normal strain components in the x 1 and x 2 directions, and (c) 33 is the out-of-plane normal strain component, normal to the interface plane in the x 3 direction. The elastic moduli near the interface are set equal to the bulk elastic moduli.…”

Section: (I) Misfit Strainsmentioning

confidence: 99%

Understanding dislocation mechanics at the mesoscale using phase field dislocation dynamics

Beyerlein

Hunter

2016

Phil. Trans. R. Soc. A.

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One contribution of 11 to a theme issue 'Trends and challenges in the mechanics of complex materials' . In this paper, we discuss the formulation, recent developments and findings obtained from a mesoscale mechanics technique called phase field dislocation dynamics (PFDD). We begin by presenting recent advancements made in modelling face-centred cubic materials, such as integration with atomic-scale simulations to account for partial dislocations. We discuss calculations that help in understanding grain size effects on transitions from full to partial dislocation-mediated slip behaviour and deformation twinning. Finally, we present recent extensions of the PFDD framework to alternative crystal structures, such as body-centred cubic metals, and two-phase materials, including free surfaces, voids and bi-metallic crystals. With several examples we demonstrate that the PFDD model is a powerful and versatile method that can bridge the length and time scales between atomistic and continuum-scale methods, providing a much needed understanding of deformation mechanisms in the mesoscale regime.

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Prediction of Dislocation Cores in Aluminum from Density Functional Theory

Cited by 165 publications

References 26 publications

Solute strengthening in random alloys

Solute strengthening in random alloys

Polymorphism of dislocation core structures at the atomic scale

Understanding dislocation mechanics at the mesoscale using phase field dislocation dynamics

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