Journal ArticleDOI
Deforming nanocrystalline nickel at ultrahigh strain rates
Yinmin Wang,Eduardo M. Bringa,James McNaney,M. Victoria,Alfredo Caro,Andrea M. Hodge,Raymond F. Smith,Ben Torralva,Bruce Remington,Christopher A. Schuh,H. Jamarkani,Marc A. Meyers +11 more
TLDR
In this paper, the deformation mechanism of nanocrystalline Ni at ultrahigh strain rates (>107s−1) was investigated, and it was shown that dislocation activity is a prevalent deformation mechanisms for the grain sizes studied.Abstract:
The deformation mechanism of nanocrystalline Ni (with grain sizes in the range of 30–100 nm) at ultrahigh strain rates (>107s−1) was investigated. A laser-driven compression process was applied to achieve high pressures (20–70 GPa) on nanosecond timescales and thus induce high-strain-rate deformation in the nanocrystalline Ni. Postmortem transmission electron microscopy examinations revealed that the nanocrystalline structures survive the shock deformation, and that dislocation activity is a prevalent deformation mechanism for the grain sizes studied. No deformation twinning was observed even at stresses more than twice the threshold for twin formation in micron-sized polycrystals. These results agree qualitatively with molecular dynamics simulations and suggest that twinning is a difficult event in nanocrystalline Ni under shock-loading conditions.read more
Citations
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Deformation twinning in nanocrystalline materials
TL;DR: In this paper, a review of deformation twinning in nanocrystalline materials is presented, including deformation twins observed by molecular dynamics simulations and experiments, twinning mechanisms, factors affecting the twinning, analytical models on the nucleation and growth of deformations, interactions between twins and dislocations, and the effects of twins on mechanical and other properties.
Journal ArticleDOI
The Hall-Petch breakdown in nanocrystalline metals: A crossover to glass-like deformation
TL;DR: In this paper, the deformation behavior of nanocrystalline Ni-W alloys is evaluated by nanoindentation techniques for grain sizes of 3-150nm, spanning both the range of classical Hall-Petch behavior as well as the regime where deviations from the Hall-petch trend are observed.
Journal ArticleDOI
Grain size, strain rate, and temperature dependence of flow stress in ultra-fine grained and nanocrystalline Cu and Al: Synthesis, experiment, and constitutive modeling
Babak Farrokh,Akhtar S. Khan +1 more
TL;DR: In this paper, the effect of temperature on stress-strain responses of mechanically milled bulk nanocrystalline (nc) fcc metals, with least amounts of imperfections, exhibiting high strength and ductility at room and different temperatures, under quasi-static and dynamic types of loading, were prepared and a comprehensive study on their post-yield mechanical properties was performed.
Journal ArticleDOI
Grain-size dependent mechanical behavior of nanocrystalline metals
Eric N. Hahn,Marc A. Meyers +1 more
TL;DR: In this article, the most important theories of grain size dependent mechanical behavior pertaining to the nanocrystalline regime were examined, for the sake of clarity, grain sizes d are commonly divided into three regimes: d>1μm, 1μm and 1-μm.
Journal ArticleDOI
Experimental and modelling investigations on strain rate sensitivity of an electrodeposited 20 nm grain sized Ni
TL;DR: In this article, a simple and straightforward equation relating m to d was proposed in aid of a simple assumption associating L with d, which implied that the enhanced m in nc Ni and its alloys with d> ∼ 6 nm should be due to the reduction of the dislocation line length.
References
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Journal ArticleDOI
The onset of twinning in metals: a constitutive description
TL;DR: In this article, a constitutive expression for the twinning stress in BCC metals is developed using dislocation emission from a source and the formation of pile-ups, as rate-controlling mechanism.
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A Maximum in the Strength of Nanocrystalline Copper
TL;DR: Using molecular dynamics simulations with system sizes up to 100 million atoms to simulate plastic deformation of nanocrystalline copper, it is shown that the flow stress and thus the strength exhibit a maximum at a grain size of 10 to 15 nanometers.
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Stacking fault energies and slip in nanocrystalline metals
TL;DR: It is shown, using molecular dynamics simulations, that the nature of slip in nanocrystalline metals cannot be described in terms of the absolute value of the stacking fault energy—a correct interpretation requires the generalized stacking faultEnergy curve, involving both stable and unstable stacking fault energies.
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Nanocrystalline electrodeposited Ni: microstructure and tensile properties
TL;DR: In this article, the microstructure of commercially available nanocrystalline (nc) electroplated Ni foils is studied by means of Xray diffraction and transmission electron microscopy.
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Plastic Deformation with Reversible Peak Broadening in Nanocrystalline Nickel
TL;DR: During plastic deformation of electrodeposited nanocrystalline nickel, the peak broadening is reversible upon unloading; hence, the deformation process does not build up a residual dislocation network.