Statistical analysis of the size- and rate-dependence of yield and plastic flow in nanocrystalline copper pillars

Lee, Jung A.; Seok, Moo Young; Zhao, Yakai; Choi, In Chul; Lee, Dong Hoon; Seo, Brandon B.; Ramamurty, Upadrasta; Tsui, Ting Y.; Jang, Jae-il

doi:10.1016/j.actamat.2017.01.033

Cited by 14 publications

(1 citation statement)

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“…For micropillars with smooth stress-strain curves, since the determination of the exact value of yield stress is difficult due to a continuous transition from elastic to elastoplastic deformation regimes of the stress-strain response, flow stress obtained by a strain offset of 1% instead of a conventional 0.2% offset stress, is designated as yield stress [30], as illustrated in Figures 4-6. For micropillars showing discontinuous flow behavior, the yield stress is identified as the stress at the first discrete displacement burst that occurred post-1% strain in each curve, and a threshold of �ε ≥ 0.002 is used to identify the burst events [31], as exhibited in Figure 7(a).…”

Section: In-situ Compression Testsmentioning

confidence: 99%

Achieving High Strength-plasticity of Nanoscale Lamellar Grain Extracted from Gradient Lamellar Nickel

Wang

Jia

Zhang

et al. 2022

Chin. J. Mech. Eng.

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Traditional metallic materials usually face a dilemma between high strength and poor strain hardening capacity. However, heterogeneous structured metallic materials have been found to obviously overcome the trade-off. Herein, gradient lamellar structure was fabricated through ultrasound-aided deep rolling technique in pure Ni with high stacking fault energy after heat treatment. The gradient lamellar Ni was successively divided into the four regions. In-situ micropillar compression tests were conducted in different regions to reveal the corresponding microscopic mechanical properties. Microscopic characterization techniques were performed to explore underlying deformation mechanisms and the effects of microstructural parameters on deformation behaviors. This work demonstrates that the micropillar with near nanoscale lamellar thickness possesses excellent strength and plasticity. On one hand, the reason for high strength of near nanoscale micropillar is that the strength of micropillar increases with the decrease of lamellar thickness according to the Hall-Petch effect. On the other hand, numerous lamellar grain boundaries perpendicular to the loading direction is found to hinder the motion of slip bands, resulting in great strain hardening capacity in the near nanoscale lamellar micropillar.

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Section: In-situ Compression Testsmentioning

confidence: 99%

Achieving High Strength-plasticity of Nanoscale Lamellar Grain Extracted from Gradient Lamellar Nickel

Wang

Jia

Zhang

et al. 2022

Chin. J. Mech. Eng.

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Enhanced strength of cyclically preloaded arrays of pillars

Derda

Domański

2020

Acta Mech

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Under compression, a cyclically precompressed nanopillar supports greater load than its as-fabricated counterpart. Such an improvement on mechanical properties takes place only when the preloading process is tuned carefully with regard to a particular pillar being tested. This experimental evidence raises a question: does a cyclic preloading applied simultaneously to an ensemble of nanopillars enhance the overall strength of the system? To answer this question, we simulate numerically cyclic loadings of pillars assembled into an array. Assuming that the pillars are characterized by random strength-thresholds $$\left\{ \sigma _{\mathrm{th}}\right\} $$ σ th , we demonstrate that quasi-statically compressed arrays with initial cycling process support higher load than the corresponding ones with no precompression. By applying the fibre bundle model, we evolve $$\left\{ \sigma _{\mathrm{th}}\right\} $$ σ th and estimate that the mean strengthening may attain 7–9% for an optimally tailored cycling.

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Grain-Size-Dependent Grain Boundary Deformation during Yielding in Nanocrystalline Materials Using Atomistic Simulations

Rajaram

Gupta

Thompson

et al. 2020

JOM

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Statistical analysis of the size- and rate-dependence of yield and plastic flow in nanocrystalline copper pillars

Cited by 14 publications

References 50 publications

Achieving High Strength-plasticity of Nanoscale Lamellar Grain Extracted from Gradient Lamellar Nickel

Achieving High Strength-plasticity of Nanoscale Lamellar Grain Extracted from Gradient Lamellar Nickel

Enhanced strength of cyclically preloaded arrays of pillars

Grain-Size-Dependent Grain Boundary Deformation during Yielding in Nanocrystalline Materials Using Atomistic Simulations

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