Plastic deformation of freestanding thin films: Experiments and modeling

Nicola, Lucia; Xiang, Yong; Vlassak, Joost J.; Giessen, van der Erik; Needleman, A.

doi:10.1016/j.jmps.2006.04.005

Cited by 211 publications

(154 citation statements)

References 42 publications

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“…Although in the present circumstances, the polycrystal specimens analysed exhibit no size effect, consistent with experimental observations, discrete dislocation analyses of free-standing polycrystalline films having a columnar type grain structure do predict a size-dependent response for sufficiently thin films [8]. There are various possible reasons for the prediction of size dependence in [8] and the prediction of size independence in the circumstances analysed in this study.…”

Section: Discussionsupporting

confidence: 86%

“…There are various possible reasons for the prediction of size dependence in [8] and the prediction of size independence in the circumstances analysed in this study. One set of possibilities concerns the number of grains across the thickness of the film and the shape of the grains: the films considered in [8] are columnar (one grain through the thickness), while the polycrystals here have at least two grains through the thickness. This affects the tendency for slip being blocked by grain boundaries normal to the tensile direction and thereby affects the development of internal stress.…”

Section: Discussionmentioning

confidence: 95%

“…This affects the tendency for slip being blocked by grain boundaries normal to the tensile direction and thereby affects the development of internal stress. Other possibilities concern the effects of grain aspect ratio, in [8] grain aspect ratios from 0.4 to 4.0 were considered while here the grain aspect ratio is fixed at 3, and the effects of differences in material properties: there are no obstacles in the simulations in Nicola et al [8]; the source density is even lower than in the LSD case analysed here and a wider distribution of source strengths was used. Which of these factors are mainly responsible for the difference in size dependence between the present results and and those in [8] remains to be identified.…”

Section: Discussionmentioning

confidence: 99%

“…These experimental results are consistent with the expectation of a size-independent response when slip is unconstrained and when the loading is compatible with an overall homogeneous deformation state. On the other hand, when slip is constrained, for example, due to grain boundaries or interfaces, a size-dependent response occurs, as in the grain size dependence of the flow strength of polycrystals (the Hall-Petch effect) and in the plastic response of thin films [5][6][7][8]. The strong size effect observed recently in the compressive response of micron-size single crystals [9][10][11] was unexpected because slip is unconstrained.…”

Section: Introductionmentioning

confidence: 99%

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Size effects in uniaxial deformation of single and polycrystals: a discrete dislocation plasticity analysis

Balint

Deshpande

Needleman

et al. 2006

Modelling Simul. Mater. Sci. Eng.

103

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The effect of specimen size on the uniaxial deformation response of planar single crystals and polycrystals is investigated using discrete dislocation plasticity. The dislocations are all of edge character and modelled as line singularities in a linear elastic material. The lattice resistance to dislocation motion, dislocation nucleation, dislocation interaction with obstacles and dislocation annihilation are incorporated through a set of constitutive rules. Grain boundaries are modelled as impenetrable to dislocations. Two types of polycrystalline materials are considered: one that only has grains with a single orientation while the other has a checker-board arrangement of two types of grains which are rotated 90 • with respect to each other. The single crystals display a strong size dependence with the flow strength increasing with decreasing specimen size. In sufficiently small single crystal specimens, the nucleation rate of the dislocations is approximately equal to the rate at which the dislocations exit the specimens so that below a critical specimen size the flow strength is set by the strength of the initially present Frank-Read sources. On the other hand, grain boundaries acting as barriers to plastic deformation in polycrystalline specimens of the same size lead to a more diffuse deformation pattern and to a nearly size-independent response.

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Section: Discussionsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 95%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Size effects in uniaxial deformation of single and polycrystals: a discrete dislocation plasticity analysis

Balint

Deshpande

Needleman

et al. 2006

Modelling Simul. Mater. Sci. Eng.

103

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“…Thus, the model explicitly incorporates the effects of grain size and orientation, as well as the piling-up of dislocations, which gives rise to size dependent plastic flow as shown previously for passivated films in Ref. 4. A recent innovation of the model in Ref.…”

Section: Introductionmentioning

confidence: 94%

Bauschinger effect in unpassivated freestanding thin films

Shishvan

Nicola

Giessen

2010

Journal of Applied Physics

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Two-dimensional ͑2D͒ discrete dislocation plasticity simulations are carried out to investigate the Bauschinger effect ͑BE͒ in freestanding thin films. The BE in plastic flow of polycrystalline materials is generally understood to be caused by inhomogeneous deformation during loading, leading to residual stress upon unloading. This inhomogeneity can be caused by dislocation pile-ups, variations in texture, grain orientations, and grain size. To study the BE, columnar-grained films as well as films with multiple grains across the thickness are considered. The film is modeled in a 2D framework by a unit cell consisting of an array of grains with different orientation. In order to capture the interaction among grains, we motivate and explore the use of an affine deformation assumption on the grain level to mimic the three-dimensional geometry in this framework. It is shown that the dispersion of grain size in a film together with the size-dependence of yield strength leads to significant BEs in bare films. Quantitative comparison of simulations with experimental data is provided.

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Size‐Dependent Strength in Single‐Crystalline Metallic Nanostructures

Greer

2012

Nano and Cell Mechanics

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Plastic deformation of freestanding thin films: Experiments and modeling

Cited by 211 publications

References 42 publications

Size effects in uniaxial deformation of single and polycrystals: a discrete dislocation plasticity analysis

Size effects in uniaxial deformation of single and polycrystals: a discrete dislocation plasticity analysis

Bauschinger effect in unpassivated freestanding thin films

Size‐Dependent Strength in Single‐Crystalline Metallic Nanostructures

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