Effect of nanocrystalline and ultrafine grain sizes on the strain rate sensitivity and activation volume: fcc versus bcc metals

Wei, Qian; Cheng, Sheng; Ramesh, K.T.; Ma, E.

doi:10.1016/j.msea.2004.03.064

Cited by 807 publications

(379 citation statements)

References 70 publications

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“…10 shows the strain-rate sensitivity m as a function of grain size for a range of grain sizes from nanocrystalline to coarse grained and for a number of different processing methods. 108,126,134,137,[149][150][151][152][153][154][155][156][157][158][159] The coefficient m increases with decreasing grain size. Moreover, this plot shows that the strain-rate sensitivities are as high as 3-4 times higher for ultrafine-grained Cu than for coarse-grained Cu and are as high as 6-8 times higher for nanocrystalline materials than for coarse-grained Cu.…”

Section: Strain-rate Sensitivity (And Activation Volume)mentioning

confidence: 99%

“…The strain-rate sensitivity m increases with decreasing grain size for copper processed by a number of different methods. The different grain sizes are categorized into nanocrystalline ( <100 nm), ultrafine grained (100 nm to 1lm), and coarse grained (>1 lm) for various studies 108,126,134,137,[149][150][151][152][153][154][155][156][157][158][159] ''Bulk'' Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys…”

Section: Strain-rate Sensitivity (And Activation Volume)mentioning

confidence: 99%

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“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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Section: Strain-rate Sensitivity (And Activation Volume)mentioning

confidence: 99%

Section: Strain-rate Sensitivity (And Activation Volume)mentioning

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

View full text Add to dashboard Cite

show abstract

“…This interaction is described by the so called PeierlsNabarro barrier. According to the comprehensive results in [18] the SRS of bcc metals decreases with a reduction of grain size, since new grain boundaries act as long-range obstacles that can not be overcome by thermal activation. For that reason, the SRS-plot implies that the interaction of moving dislocations with short range obstacles drops significantly already for considerably low strains and even disappears for strains of ~15.…”

Section: Nanomaterials By Severe Plastic Deformation IVmentioning

confidence: 99%

Ultimate Strength of a Tungsten Heavy Alloy after Severe Plastic Deformation at Quasi-Static and Dynamic Loading

Meyer

Hockauf

Hohenwarter

et al. 2008

MSF

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Abstract. A tungsten heavy alloy (92%W, Ni-Co matrix) is subjected to severe plastic deformation (SPD) by high pressure torsion (HPT) at room temperature up to equivalent strains of 0.7, 5.3, 10.7 and 14.3. The microstructure and the mechanical properties are investigated by cylindrical compression samples at quasi-static and dynamic loading. The harder spherical W particles are homogeneously deformed within the softer matrix, becoming ellipsoidal at medium strains and banded at high strains without shear localization or fracture. Results of quasi-static loading show that the strength is approaching a limiting value at strains of ~10. At this strain for the matrix a grain size of ~80 nm and for W a cell size of ~250 nm was observed, suggesting strain concentration on the matrix. The initial yield stress of 945 MPa for the coarse-grained condition is increased thereby to an ultimate value of 3500 MPa, while a peak stress of ~3600 MPa is reached. Such remarkably strength has never been reported before for pure W or W-based composites. The strain hardening capacity as well as the strain rate sensitivity is reduced drastically, promoting the early formation of (adiabatic) shear bands.

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“…For the C/A multilayer composites, their thermally-activated plastic deformation mechanisms can also be revealed by quantifying their SRS. Thus, various methods have been developed for determining SRS in the past few decades [15][16][17][18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

“…Macroscopically, the SRS is often measured by uniaxial tension [15][16][17][18][19][20] and compression tests [21,22] on bulk specimens, whereas nanoindentation is widely adopted to measure SRS of small specimens, such as thin films. Figure 1 illustrates the differences between SRS measurement under tension/compression and nanoindentation.…”

Section: Introductionmentioning

confidence: 99%

Thickness-Dependent Strain Rate Sensitivity of Nanolayers via the Nanoindentation Technique

et al. 2018

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Abstract:The strain rate sensitivity (SRS) and dislocation activation volume are two inter-related material properties for understanding thermally-activated plastic deformation, such as creep. For face-centered-cubic metals, SRS normally increases with decreasing grain size, whereas the opposite holds for body-center-cubic metals. However, these findings are applicable to metals with average grain sizes greater than tens of nanometers. Recent studies on mechanical behaviors presented distinct deformation mechanisms in multilayers with individual layer thickness of 20 nanometers or less. It is necessary to estimate the SRS and plastic deformation mechanisms in this regime. Here, we review a new nanoindentation test method that renders reliable hardness measurement insensitive to thermal drift, and its application on SRS of Cu/amorphous-CuNb nanolayers. The new technique is applied to Cu films and returns expected SRS values when compared to conventional tensile test results. The SRS of Cu/amorphous-CuNb nanolayers demonstrates two distinct deformation mechanisms depending on layer thickness: dislocation pileup-dominated and interface-mediated deformation mechanisms.

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Effect of nanocrystalline and ultrafine grain sizes on the strain rate sensitivity and activation volume: fcc versus bcc metals

Cited by 807 publications

References 70 publications

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

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

Ultimate Strength of a Tungsten Heavy Alloy after Severe Plastic Deformation at Quasi-Static and Dynamic Loading

Thickness-Dependent Strain Rate Sensitivity of Nanolayers via the Nanoindentation Technique

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