Yield maps for nanoscale metallic multilayers

Lamm, Adrienne V.; Anderson, Peter M.

doi:10.1016/j.scriptamat.2003.11.040

Cited by 12 publications

(9 citation statements)

References 16 publications

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“…Email: mughrabi@ww.uni-erlangen.de unpassivated; compare, for example, the work of Freund [1], Nix [2,3] or of Embury (to whom this article is dedicated) and Hirth [4]. The macroyielding of two-phase multilayered thin films [5] is another example of constrained dislocation glide. In many of the early studies only the behaviour of a single dislocation segment was considered.…”

Section: Introductionmentioning

confidence: 99%

Constrained glide and interaction of bowed-out screw dislocations in confined channels

Mughrabi¹,

Pschenitzka²

2005

Philosophical Magazine

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In the present work, a particular case of constrained dislocation glide that is typical of deformation in small volumes as, for example, in thin films was studied. The specific problem addressed concerns the glide and interaction of two unlike screw dislocations bowing out in constrained channels on parallel glide planes. The situation described corresponds not only to thin film deformation but also to the constrained glide of dislocations in the channels between the dislocation walls in persistent slip bands (PSBs) in fatigued metals. The main objective of the study was to determine the flow stress and to assess in an analytic approximation how the contributions of the dipolar interaction stress and of the bowing stress which both vary in space superimpose. It was argued that the dipolar interaction between the two dislocations is overcome by 'bowing-out' and not by separation of the aligned dislocation dipole 'at constant shape'. A general conclusion of the numerical analysis is that, aside from one trivial irrelevant case, the resulting flow stress is never a simple linear sum of the Orowan bowing stress and the dipole passing stress. Rather, the flow stress is always governed by the stronger of the two interactions and is, typically, at most ca. 20% larger than either the Orowan stress or the dipole passing stress, depending on which of the two is larger. The numerical results are discussed briefly with respect to an idealized example of dislocation glide in thin films and in more detail with regard to dislocation glide in the channels of PSBs. In the latter case, the present results match nicely with the interpretation of the cyclic flow stress of PSBs in terms of the so-called composite model which considers explicitly the weighted contributions of the local flow stresses in the relatively soft channels and in the harder dislocation walls to the overall stress.

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Section: Introductionmentioning

confidence: 99%

Constrained glide and interaction of bowed-out screw dislocations in confined channels

Mughrabi¹,

Pschenitzka²

2005

Philosophical Magazine

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“…In some cases, yield is defined by the macroscopic stress to eliminate an alternating tensile/compressive stress state between A/B layers, arising from a mismatch in the stress-free lattice parameters of A and B layers [223,243,244]. Other models require overcoming the energetic force on dislocations arising from a mismatch in elastic modulus between A and B layers [190].…”

Section: Deformation Mechanismsmentioning

confidence: 99%

“…Others combine internal stress state with continuity of slip planes across the interface [246,247]. Deviations from estimates of strength due to lattice parameter and/or elastic modulus mismatch are sometimes attributed to an interfacial strength dependent on interfacial dislocation content, dislocation core spreading at interfaces, and continuity of slip planes across interface [230,231,243,248,249]. Estimates of core spreading and other effects vary and are difficult to correlate with experimental data [230,231,243,248].…”

Section: Deformation Mechanismsmentioning

confidence: 99%

Mechanical Properties of Nanostructured Metals

Anderson

Carpenter

Gram

et al. 2014

Handbook of Nanomaterials Properties

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PolycrystalsThis section is divided into four subsections. The subsection on synthesis and structure treats electrodeposition, severe plastic deformation, and mechanical alloying. It highlights features that affect mechanical properties such as texture, grain size and shape, internal stress, twinning, dislocations, and point defects. The mechanical properties subsection contrasts yield strength, ductility, strain hardening, strain-rate sensitivity, creep, and fatigue in conventional versus nanocrystalline metals. Underlying deformation mechanisms are then discussed in terms of deformation-mechanism maps and intragranular slip versus grain-boundarymediated regimes. Finally, modeling and simulation approaches are presented in terms of atomistic versus continuum methods.

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“…This abrupt change is attributed to the inability of interfaces and grain boundaries to confine dislocation loops to diminishingly small volumes of material. Thus, ultimate strength at the nanometer scale and various simulations to model dislocation confinement (Gillard et al, 1994;Anderson and Li, 1995;Pant et al, 2003;Lamm and Anderson, 2004;Li and Anderson, 2005;Ghoniem and Han, 2005) hinge on the strength of grain boundaries or interfaces to slip transmission.…”

Section: Introductionmentioning

confidence: 99%