Screw dislocation mobility in BCC metals: the role of the compact core on double-kink nucleation

Gordon, Peter A.; Neeraj, T.; Li, Y; Li, J

doi:10.1088/0965-0393/18/8/085008

Cited by 90 publications

(74 citation statements)

References 37 publications

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“…While this result may not appear at first to be very surprising as a sinusoidal potential is an obvious choice, Hirth and Lothe 32 have pointed out that this is a model potential and may not accurately describe the potential shape in real materials. Furthermore, the empirical potentials, as noted here and shown in other studies 15,16 , often predict a double maximum (camel hump) Peierls potential. Thus, the prediction of a common sinusoidal potential may be regarded as quite surprising.…”

Section: B Dft Predictionssupporting

confidence: 81%

“…This is in agreement with recent DFT calculations of the core structure in iron 23 that showed a Peierls potential that is sinusoidal in shape and lacks a metastable split core structure. These results suggest that empirical potentials are often incorrect, as they frequently predict either a degenerate core structure or a compact core structure along with the split core structure 15 . It therefore seems prudent to use the Peierls potential as either part of interatomic potential development in BCC metals or as part of their validation if the potentials are meant to predict properties of BCC screw dislocations, an approach recently taken for the development of BCC iron potentials 54 .…”

Section: Discussionmentioning

confidence: 99%

“…Specifically, these simulations have shown two possible types of equilibrium core structures 5 , the compact core which exhibits the full D3 symmetry of the 111 zone, and the polarized core which only exhibits C3 symmetry (the three-fold rotation axis) and therefore has two degenerate structures related through the 110 diad. In addition to the predictions of two different equilibrium core structures, these empirical potentials often predict an additional metastable core position 15 , the split core 16 , to exist between two equivalent compact core structures. This dislocation core lies on a specific {110} plane, only obeys the diad symmetry, and is triply degenerate.…”

Section: Introductionmentioning

confidence: 99%

“…This dislocation core lies on a specific {110} plane, only obeys the diad symmetry, and is triply degenerate. The existence of the split core structure means there is an additional metstable state as the screw dislocation moves from one compact core to another, which allows for the nucleation of partial kinks along the dislocation line, results in discontinuities in the activation enthalpy as a function of stress 10,[15][16][17] , and creates a tendency for {112} slip 18 . To better understand plasticity in BCC transition metals, recently density functional theory (DFT) has been used to determine dislocation core structures, Peierls stress, and sometimes Peierls potentials.…”

Section: Introductionmentioning

confidence: 99%

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Peierls potential of screw dislocations in bcc transition metals: Predictions from density functional theory

2013

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It is well known that screw dislocation motion dominates the plastic deformation in body-centeredcubic metals at low temperatures. The nature of the non-planar structure of screw dislocations gives rise to high lattice friction which results in strong temperature and strain rate dependence of plastic flow. Thus, the nature of the Peierls potential, which is responsible for the high lattice resistance, is an important physical property of the material. However, current empirical potentials give a complicated picture of the Peierls potential. Here, we investigate the nature of the Peierls potential using Density Functional Theory in the BCC transition metals. The results show that the shape of the Peierls potential is sinusoidal for every material investigated. Furthermore, we show the magintiude of the potential scales strongly with the energy per-unit-length of the screw dislocation in the material.

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Section: B Dft Predictionssupporting

confidence: 81%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Peierls potential of screw dislocations in bcc transition metals: Predictions from density functional theory

2013

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“…In the literature various studies can be found to deal with the dislocation mobility using molecular dynamics simulations. However, they are all limited to simple systems and they do not attempt to calculate the effect of the concentration on the mobility [42][43][44]. Recently work has been done in calculating the mobility of screw dislocations in α-iron and to derive analytical expressions for the use within the dislocation dynamics [45].…”

Section: Introductionmentioning

confidence: 99%

Large Scale DD Simulation Results for Crystal Plasticity Parameters in Fe-Cr And Fe-Ni Systems

Zbib¹,

Li²,

Sun³

et al. 2012

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SUMMARYThe development of viable nuclear energy source depends on ensuring structural materials integrity. Structural materials in nuclear reactors will operate in harsh radiation conditions coupled with high level hydrogen and helium production, as well as formation of high density of point defects and defect clusters, and thus will experience severe degradation of mechanical properties. Therefore, the main objective of this work is to develop a capability that predicts aging behavior and in-service lifetime of nuclear reactor components and, thus provide an instrumental tool for tailoring materials design and development for application in future nuclear reactor technologies. Towards this end goal, the long term effort is to develop a physics-based multiscale modeling hierarchy, validated and verified, to address outstanding questions regarding the effects of irradiation on materials microstructure and mechanical properties during extended service in the fission and fusion environments. The focus of the current investigation is on modern steels for use in nuclear reactors including high strength ferritic-martensitic steels (Fe-Cr-Ni alloys).The effort is to develop a predictive capability for the influence of irradiation on mechanical behavior. Irradiation hardening is related to structural information crossing different length scales, such as composition, dislocation, and crystal orientation distribution. To predict effective hardening, the influence factors along different length scales should be considered. Therefore, a hierarchical upscaling methodology is implemented in this work in which relevant information is passed between models at three scales, namely, from molecular dynamics to dislocation dynamics to dislocation-based crystal plasticity. The molecular dynamics (MD) was used to predict the dislocation mobility in body centered cubic (bcc) Fe and its Ni and Cr alloys. The results are then passed on to dislocation dynamics to predict the critical resolved shear stress (CRSS) from the evolution of local dislocation and defects.In this report the focus is on the results obtained from large scale dislocation dynamics simulations. The effects of defect density and materials structure were investigated while new evolution laws were proposed. These results will form the bases for the development of evolution and hardening laws for a dislocation-based crystal plasticity framework. The hierarchical upscaling method being developed in this project can provide a guidance tool to evaluate performance of structural materials for nextgeneration nuclear reactors. Combined with other tools developed in the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program, the models developed will have more impact in improving the reliability of current reactors and affordability of new reactors.

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Simulating Dislocation Plasticity inBCCMetals by Integrating Fundamental Concepts with Macroscale Models

Lim

Battaile

Weinberger

2018

Integrated Computational Materials Engineering (ICME) for Metals

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Screw dislocation mobility in BCC metals: the role of the compact core on double-kink nucleation

Cited by 90 publications

References 37 publications

Peierls potential of screw dislocations in bcc transition metals: Predictions from density functional theory

Peierls potential of screw dislocations in bcc transition metals: Predictions from density functional theory

Large Scale DD Simulation Results for Crystal Plasticity Parameters in Fe-Cr And Fe-Ni Systems

Simulating Dislocation Plasticity inBCCMetals by Integrating Fundamental Concepts with Macroscale Models

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