Plasticity of Micrometer-Scale Single Crystals in Compression

Uchic, Michael D.; Shade, Paul A.; Dimiduk, Dennis M.

doi:10.1146/annurev-matsci-082908-145422

Cited by 708 publications

(493 citation statements)

References 76 publications

(140 reference statements)

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“…22 Plasticity of micro/nano-pillars has been extensively studied in recent years. 22,23 In general, strength increases as the pillar diameter decreases. For micropillars, plasticity occurs through the activation of single-arm sources (or truncated Frank-Read sources).…”

Section: Resultsmentioning

confidence: 99%

Size effects on elasticity, yielding, and fracture of silver nanowires:In situexperiments

et al. 2012

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This paper reports the first quantitative measurement of a full spectrum of mechanical properties of five-fold twinned silver (Ag) nanowires (NWs) including Young's modulus, yield strength and ultimate tensile strength. In situ tensile testing of Ag NWs with diameters between 34 and 130 nm was carried out inside a scanning electron microscope (SEM). Young's modulus, yield strength and ultimate tensile strength all increased as the NW diameter decreased. The maximum yield strength in our tests was found to be 2.64 GPa, which is about 50 times the bulk value and close to the theoretical value of Ag in the <110> orientation. The size effect in the yield strength is attributed to the increase in the Young's modulus. Yield strain scales reasonably well with the NW surface area, which reveals that yielding of Ag NWs is due to dislocation nucleation from surface sources. Pronounced strain hardening was observed for most NWs in our study. The strain hardening, which has not previously been reported for NWs, is mainly attributed to the presence of internal twin boundaries. KEYWORDSfive-fold twin, size effect, Young's modulus, yield strength, ultimate tensile strength, strain hardening

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Section: Resultsmentioning

confidence: 99%

Size effects on elasticity, yielding, and fracture of silver nanowires:In situexperiments

et al. 2012

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“…In fact, for many of these techniques, innovative setups are pushing the lower bound of the specimen sizes. 109,110 Some of the following discussion is based in part on the review of mechanical properties of nanocrystalline materials by Meyers et al 4 Mechanical Properties…”

Section: Physical and Mechanical Properties Of Nanocrystalline Materialsmentioning

confidence: 99%

“Bulk” Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys

Tschopp

Murdoch

Kecskes

et al. 2014

JOM

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It is a new beginning for innovative fundamental and applied science in nanocrystalline materials. Many of the processing and consolidation challenges that have haunted nanocrystalline materials are now more fully understood, opening the doors for bulk nanocrystalline materials and parts to be produced. While challenges remain, recent advances in experimental, computational, and theoretical capability have allowed for bulk specimens that have heretofore been pursued only on a limited basis. This article discusses the methodology for synthesis and consolidation of bulk nanocrystalline materials using mechanical alloying, the alloy development and synthesis process for stabilizing these materials at elevated temperatures, and the physical and mechanical properties of nanocrystalline materials with a focus throughout on nanocrystalline copper and a nanocrystalline Cu-Ta system, consolidated via equal channel angular extrusion, with properties rivaling that of nanocrystalline pure Ta. Moreover, modeling and simulation approaches as well as experimental results for grain growth, grain boundary processes, and deformation mechanisms in nanocrystalline copper are briefly reviewed and discussed. Integrating experiments and computational materials science for synthesizing bulk nanocrystalline materials can bring about the next generation of ultrahigh strength materials for defense and energy applications.

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“…Then, the smooth σ − curves are interpreted as resulting from the averaging process of the dislocation activity in the sample. Indeed, the intermittent character of dislocation motion at the microscopic level is reflected in the strong stress fluctuations seen in nanometer sized samples that are not seen in macroscopic samples [26].…”

Section: Introductionmentioning

confidence: 99%

General framework for acoustic emission during plastic deformation

2015

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Despite the long history, so far there is no general theoretical framework for calculating the acoustic emission spectrum accompanying any plastic deformation. We set up a discrete wave equation with plastic strain rate as a source term and include the Rayleigh-dissipation function to represent dissipation accompanying acoustic emission. We devise a method of bridging the widely separated time scales of plastic deformation and elastic degrees of freedom. While this equation is applicable to any type of plastic deformation, it should be supplemented by evolution equations for the dislocation microstructure for calculating the plastic strain rate. The efficacy of the framework is illustrated by considering three distinct cases of plastic deformation. The first one is the acoustic emission during a typical continuous yield exhibiting a smooth stress-strain curve. We first construct an appropriate set of evolution equations for two types of dislocation densities and then show that the shape of the model stress-strain curve and accompanying acoustic emission spectrum match very well with experimental results. The second and the third are the more complex cases of the Portevin-Le Chatelier bands and the Lüders band. These two cases are dealt with in the context of the Ananthakrishna model since the model predicts the three types of the Portevin-Le Chatelier bands and also Lüders-like bands. Our results show that for the type-C bands where the serration amplitude is large, the acoustic emission spectrum consist of well separated bursts of acoustic emission. At higher strain rates of hopping type-B bands, the burst type acoustic emission spectrum tends to overlap forming a nearly continuous background with some sharp acoustic emission bursts. The latter can be identified with the nucleation of new bands. The acoustic emission spectrum associated with the continuously propagating type-A band is continuous. These predictions are consistent with experimental results. More importantly, our study shows that the low amplitude continuous acoustic emission spectrum seen in both the type-B and A band regimes is directly correlated to small amplitude serrations induced by propagating bands. The acoustic emission spectrum of the Lüders-like band matches with recent experiments as well. In all of these cases, acoustic emission signals are burst-like reflecting the intermittent character of dislocation mediated plastic flow.

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Plasticity of Micrometer-Scale Single Crystals in Compression

Cited by 708 publications

References 76 publications

Size effects on elasticity, yielding, and fracture of silver nanowires:In situexperiments

Size effects on elasticity, yielding, and fracture of silver nanowires:In situexperiments

“Bulk” Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys

General framework for acoustic emission during plastic deformation

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