Atomistic simulation of kink-pairs of screw dislocations in body-centred cubic iron

Wen, Mei; Ngan, A.H.W.

doi:10.1016/s1359-6454(00)00288-3

Cited by 68 publications

(60 citation statements)

References 13 publications

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“…Screw dislocations have low mobility because their cores are non-planar. By atomistic simulation of the kink-pair mechanisms in screw dislocations in BCC iron, Wen & Ngan (2000) have found that if a pure screw dislocation is forced to move, its motion cannot continue on a single slip plane because of the asymmetry of the kink-pairs involved, but instead, it will have to cross-slip on every atomic step. From the above, we can postulate the formation mechanism of microbands, which hinges on the fact that the habit plane of a microband has the largest Schmid factor, as follows.…”

Section: (B) Dislocation Mechanism Of Microband Formationmentioning

confidence: 99%

Microstructure evolution in an interstitial-free steel during cold rolling at low strain levels

Chen

Ngan

Duggan

2003

Proc. R. Soc. Lond. A

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Microstructure development in an interstitial-free steel during cold rolling at low strain levels (ε 9.8%) has been investigated by using transmission electron microscopy. At a strain of 2.2%, {112} slip systems operate in addition to {110} slip planes. Dislocation reactions occur at this stage to produce immobile 100 segments in the scissors configuration and these segments are also found at higher strain in the dislocation walls of microbands. The formation of microbands starts at small reductions (ε ∼ 6.7%), and microbands are of lenticular shapes and have habit planes running approximately parallel to {110} planes. Two sets of dislocations comprise the microband walls; one is predominant and has its Burgers vector lying on the microband's habit plane. The secondary set is much less dense, and its slip plane is not coplanar with the microband habit plane. A considerable misorientation exists between the inner region of a microband and either of its two neighbouring matrices, rather than between the two matrices, which is consistent with Jackson's double cross-slip model. However, the growing end of a microband indicates the splitting of a dense dislocation sheet. In the specimen that was rolled to ε = 9.8%, some grains contain one or two sets of microbands, while some are microband-free.The crystallographic measurement and deformation geometry calculation reveal that the habit plane of an observed microband has the largest Schmid factor; and when one 111 slip direction is intensively activated in this plane, one set of microbands is formed on this plane. Two sets of microbands form if two 111 slip directions have high and nearly equal shear stresses. In the case of microband-free crystals, up to seven slip systems have similar Schmid factors and thus are activated concurrently. This leads to homogeneous deformation and as a result, no microbands form. Based on these results, a new mechanism is proposed for microband formation involving double cross-slip, dislocation wall splitting and dislocation exchange between the walls.

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Section: (B) Dislocation Mechanism Of Microband Formationmentioning

confidence: 99%

Microstructure evolution in an interstitial-free steel during cold rolling at low strain levels

Chen

Ngan

Duggan

2003

Proc. R. Soc. Lond. A

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“…In contrast, dislocations in close-packed metals on close-packed planes as well as edge dislocations in BCC metals all have low lattice resistance and high mobility [7][8][9] . Thus, extensive work exists in establishing the nature of plastic flow in BCC metals as it relates to the structure of the screw dislocation 6,[10][11][12][13][14] . Empirical atomistic models have been instrumental in confirming the theory of thermally activated flow in BCC metals as well as establishing the core structure of screw dislocations.…”

Section: Introductionmentioning

confidence: 99%

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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“…Several investigations were dedicated to the modelling of the DK mechanism (Domain and Monnet, 2005;Louchet and Kubin, 1979;Wen and Ngan, 2000;Yang and Moriarty, 2001). The main objective was to deduce the activation energy of the formation of the DK as a function of the effective stress.…”

Section: Introductionmentioning

confidence: 99%

Low temperature deformation in iron studied with dislocation dynamics simulations

Naamane

Monnet

Devincre

2010

International Journal of Plasticity

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Atomistic simulation of kink-pairs of screw dislocations in body-centred cubic iron

Cited by 68 publications

References 13 publications

Microstructure evolution in an interstitial-free steel during cold rolling at low strain levels

Microstructure evolution in an interstitial-free steel during cold rolling at low strain levels

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

Low temperature deformation in iron studied with dislocation dynamics simulations

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