Dislocation dynamics analysis of dislocation intersections in nanoscale metallic multilayered composites

Akasheh, Firas; Zbib, Hussein M.; Hirth, J. P.; Hoagland, R. G.; Misra, Amit

doi:10.1063/1.2721093

Cited by 91 publications

(23 citation statements)

References 36 publications

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“…In thin films, the Burgers vectors of dislocations adjusting the lattice mismatch between the layer and the substrate are often parallel to the interface (Demkowicz & Hoagland, 2008) and, similarly, the Burgers vectors in multilayer structures are usually parallel to the interfaces between the individual layers (Akasheh et al, 2007;Levay et al, 1999). Most of the Burgers vectors found for the h100i-and h111i-textured specimens in this work are parallel to the interface.…”

Section: à3mentioning

confidence: 59%

Dislocation density and Burgers vector population in fiber-textured Ni thin films determined by high-resolution X-ray line profile analysis

et al. 2012

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Nanocrystalline Ni thin films have been produced by direct current electrodeposition with different additives and current density in order to obtain h100i, h111i and h211i major fiber textures. The dislocation density, the Burgers vector population and the coherently scattering domain size distribution are determined by high-resolution X-ray diffraction line profile analysis. The substructure parameters are correlated with the strength of the films by using the combined Taylor and Hall-Petch relations. The convolutional multiple whole profile method is used to obtain the substructure parameters in the different coexisting texture components. A strong variation of the dislocation density is observed as a function of the deposition conditions.

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Section: à3mentioning

confidence: 59%

Dislocation density and Burgers vector population in fiber-textured Ni thin films determined by high-resolution X-ray line profile analysis

et al. 2012

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“…The high strengths and shorter dislocation lengths can help to turn on alternative slip behavior that is not common in bulk materials (37,38). In essence, small dimensions lead to high strengths that can activate secondary deformation mechanisms that make the deformation more uniform by promoting latent hardening and dislocation storage, leading to high ductility.…”

Section: Discussionmentioning

confidence: 99%

Reducing deformation anisotropy to achieve ultrahigh strength and ductility in Mg at the nanoscale

Qi²,

Mishra

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

117

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In mechanical deformation of crystalline materials, the critical resolved shear stress (CRSS; τ CRSS ) is the stress required to initiate movement of dislocations on a specific plane. In plastically anisotropic materials, such as Mg, τ CRSS for different slip systems differs greatly, leading to relatively poor ductility and formability. However, τ CRSS for all slip systems increases as the physical dimension of the sample decreases to approach eventually the ideal shear stresses of a material, which are much less anisotropic. Therefore, as the size of a sample gets smaller, the yield stress increases and τ CRSS anisotropy decreases. Here, we use in situ transmission electron microscopy mechanical testing and atomistic simulations to demonstrate that τ CRSS anisotropy can be significantly reduced in nanoscale Mg single crystals, where extremely high stresses (∼2 GPa) activate multiple deformation modes, resulting in a change from basal slip-dominated plasticity to a more homogeneous plasticity. Consequently, an abrupt and dramatic size-induced "brittleto-ductile" transition occurs around 100 nm. This nanoscale change in the CRSS anisotropy demonstrates the powerful effect of sizerelated deformation mechanisms and should be a general feature in plastically anisotropic materials.lightweight alloys | metallurgy | mechanical properties | in situ TEM | nanoparticle S trength and ductility are critical performance indicators of materials; in metals, both are associated with the activities of line defects in the crystalline lattice, called dislocation plasticity. Ductility is accomplished by the distributed and uniform multiplication and propagation of dislocations, whereas strengthening is often achieved by hindering their motion. Strength and ductility are fundamentally linked in materials, and a mechanism to improve one almost always leads to a decrease in the other (1, 2). How to achieve both high strength and high ductility is still a challenge of great importance in structural materials. Recent work has demonstrated that it is possible to improve both strength and ductility simultaneously, but this has mostly been limited to systems with ultrafine microstructures, such as nanotwinned Cu or twinning-induced plasticity steels (3, 4).As the lightest structural metal, Mg suffers from limited room temperature ductility and formability due to the highly anisotropic critical resolved shear stress (CRSS; τ CRSS ) of the different slip systems (5). In Mg, which has a hexagonal close-packed structure, the τ CRSS for nonbasal (prismatic and/or pyramidal) slip is ∼10 2 τ CRSS for basal slip (6, 7). Such an extreme plastic anisotropy of A ≡ τ nonbasal CRSS =τ basal CRSS ∼ 10 2 makes nonbasal slip very difficult to trigger. Without nonbasal slip or twinning (8), basal slip alone cannot accommodate arbitrary shape changes, and excessive basal slip in combination with unrelaxed tensile stresses in the plane-normal direction leads to spatially localized damage and rapid failure. Thus, a materials design strategy could be to enhanc...

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“…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: 96%

“…For CLS to occur, this work must exceed the energy, 2e dx, associated with depositing additional dislocation lines with energy per length e [198,[230][231][232][233][234]. This furnishes a critical stress t CLS ¼ 2e/bh.…”

Section: Deformation Mechanismsmentioning

confidence: 98%

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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Dislocation dynamics analysis of dislocation intersections in nanoscale metallic multilayered composites

Cited by 91 publications

References 36 publications

Dislocation density and Burgers vector population in fiber-textured Ni thin films determined by high-resolution X-ray line profile analysis

Dislocation density and Burgers vector population in fiber-textured Ni thin films determined by high-resolution X-ray line profile analysis

Reducing deformation anisotropy to achieve ultrahigh strength and ductility in Mg at the nanoscale

Mechanical Properties of Nanostructured Metals

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