Size effects in Al nanopillars: Single crystalline vs. bicrystalline

Kunz, Allison; Pathak, Siddhartha; Greer, Julia R.

doi:10.1016/j.actamat.2011.03.065

Cited by 167 publications

(111 citation statements)

References 65 publications

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“…The direct observation of dislocation absorption by ITBs validates a prior hypothesis by Kunz et al 34 that ITBs might be defect sinks formulated from ex situ compression studies of Al micropillars. However, both Kunz et al 34 and Ng and Ngan 35 were puzzled by the lack of dislocation pile ups along grain boundaries in deformed Al micropillars. This may be because their TEM samples were taken from excessively deformed micropillars.…”

Section: Itbsupporting

confidence: 68%

“…Discrete dislocation dynamics simulations predicted that dislocation avalanches are a universal phenomenon during deformation of single-crystal Al, and grain boundaries in polycrystalline Al would reduce avalanche frequency 33 . Micropillar compression tests on Al yield controversial results 34,35 presumably related to the orientation of grain boundaries. The initial dislocation density in nt Al was low, and subsequent deformation at greater stress triggered frequent nucleation events, suggesting dislocation nucleation-dominated strain hardening in nt Al during early stages of deformation.…”

Section: Itbmentioning

confidence: 99%

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In situ nanoindentation study on plasticity and work hardening in aluminium with incoherent twin boundaries

et al. 2014

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Nanotwinned metals have been the focus of intense research recently, as twin boundaries may greatly enhance mechanical strength, while maintaining good ductility, electrical conductivity and thermal stability. Most prior studies have focused on low stacking-fault energy nanotwinned metals with coherent twin boundaries. In contrast, the plasticity of twinned high stacking-fault energy metals, such as aluminium with incoherent twin boundaries, has not been investigated. Here we report high work hardening capacity and plasticity in highly twinned aluminium containing abundant S3{112} incoherent twin boundaries based on in situ nanoindentation studies in a transmission electron microscope and corresponding molecular dynamics simulations. The simulations also reveal drastic differences in deformation mechanisms between nanotwinned copper and twinned aluminium ascribed to stacking-fault energy controlled dislocation-incoherent twin boundary interactions. This study provides new insight into incoherent twin boundary-dominated plasticity in high stacking-fault energy twinned metals.

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Section: Itbsupporting

confidence: 68%

Section: Itbmentioning

confidence: 99%

In situ nanoindentation study on plasticity and work hardening in aluminium with incoherent twin boundaries

et al. 2014

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“…This novel, although already popular technique, is ideal for quantifying the stress-strain curve in compression of small volumes of material [24][25][26][27][28], and it has recently been extended to high temperatures in monolithic materials such as Si and Au [29,30]. Mechanical tests were complemented with detailed transmission electron microscopy (TEM) analysis of the deformed micropillars to elucidate the effect of temperature on the deformation mechanisms at the nanometer scale.…”

Section: Introductionmentioning

confidence: 99%

High temperature micropillar compression of Al/SiC nanolaminates

et al. 2013

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The effect of the temperature on the compressive stress-strain behavior of Al/SiC nanoscale multilayers was studied by means of micropillar compression tests at 23 °C and 100 °C. The multilayers (composed of alternating layers of 60 nm in thickness of nanocrystalline A1 and amorphous SiC) showed a very large hardening rate at 23 °C, which led to a flow stress of 3.1 ± 0.2 GPa at 8% strain. However, the flow stress (and the hardening rate) was reduced by 50% at 100 °C. Plastic deformation of the A1 layers was the dominant deformation mechanism at both temperatures, but the A1 layers were extruded out of the micropillar at 100 °C, while A1 plastic flow was constrained by the SiC elastic layers at 23 °C. Finite element simulations of the micropillar compression test indicated the role played by different factors (flow stress of Al, interface strength and friction coefficient) on the mechanical behavior and were able to rationalize the differences in the stress-strain curves between 23 °C and 100 °C.

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“…Analogous to the micrometer-sized Al pillars containing a vertical GB intersecting the top surface in Ng's work, Kunz et al investigated Al pillars with diameters ranging from 400 nm-1000 nm [35]. However, these submicron bi-crystalline Al pillars exhibited intermittent strain bursts, as shown in Figure 5.…”

confidence: 99%

Strategies to Approach Stabilized Plasticity in Metals with Diminutive Volume: A Brief Review

Mukherjee

Schoenung

et al. 2016

Crystals

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Abstract:Micrometer-or submicrometer-sized metallic pillars are widely studied by investigators worldwide, not only to provide insights into fundamental phenomena, but also to explore potential applications in microelectromechanical system (MEMS) devices. While these materials with a diminutive volume exhibit unprecedented properties, e.g., strength values that approach the theoretical strength, their plastic flow is frequently intermittent as manifested by strain bursts, which is mainly attributed to dislocation activity at such length scales. Specifically, the increased ratio of free surface to volume promotes collective dislocation release resulting in dislocation starvation at the submicrometer scale or the formation of single-arm dislocation sources (truncated dislocations) at the micrometer scale. This article reviews and critically assesses recent progress in tailoring the microstructure of pillars, both extrinsically and intrinsically, to suppress plastic instabilities in micrometer or submicrometer-sized metallic pillars using an approach that involves confining the dislocations inside the pillars. Moreover, we identify strategies that can be implemented to fabricate submicrometer-sized metallic pillars that simultaneously exhibit stabilized plasticity and ultrahigh strength.

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Size effects in Al nanopillars: Single crystalline vs. bicrystalline

Cited by 167 publications

References 65 publications

In situ nanoindentation study on plasticity and work hardening in aluminium with incoherent twin boundaries

In situ nanoindentation study on plasticity and work hardening in aluminium with incoherent twin boundaries

High temperature micropillar compression of Al/SiC nanolaminates

Strategies to Approach Stabilized Plasticity in Metals with Diminutive Volume: A Brief Review

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