Grain-size dependent hardening and softening of nanocrystalline Cu and Pd

Fougere, G.E.; Weertman, J.; Siegel, Richard W.; Kim, S.

doi:10.1016/0956-716x(92)90052-g

Cited by 195 publications

(58 citation statements)

References 8 publications

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“…31 Since then, there have been numerous observations of softening at very small grain sizes. [32][33][34] The reverse Hall-Petch effect seems to depend strongly on the sample preparation technique used and on the sample history, perhaps indicating that in most cases the reverse Hall-Petch effect is caused by various kinds of defects in the samples. Surface defects alone have been shown to be able to decrease the strength of nanocrystalline metals by a factor of 5, 58,66 and recent studies have shown that even very small amounts of porosity can have a dramatic effect on the strength.…”

Section: B Reverse Hall-petch Effectmentioning

confidence: 99%

“…There are a number of observations of a reverse Hall-Petch effect, i.e., of a softening when the grain size is reduced. [31][32][33][34] The interpretation of these results have generated some controversy. It is at present not clear if the experimentally reported reverse Hall-Petch effect is an intrinsic effect or if it is caused by reduced sample quality at the finest grain sizes.…”

Section: Introductionmentioning

confidence: 99%

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Atomic-scale simulations of the mechanical deformation of nanocrystalline metals

et al. 1999

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Nanocrystalline metals, i.e., metals in which the grain size is in the nanometer range, have a range of technologically interesting properties including increased hardness and yield strength. We present atomic-scale simulations of the plastic behavior of nanocrystalline copper. The simulations show that the main deformation mode is sliding in the grain boundaries through a large number of uncorrelated events, where a few atoms ͑or a few tens of atoms͒ slide with respect to each other. Little dislocation activity is seen in the grain interiors. The localization of the deformation to the grain boundaries leads to a hardening as the grain size is increased ͑reverse Hall-Petch effect͒, implying a maximum in hardness for a grain size above the ones studied here. We investigate the effects of varying temperature, strain rate, and porosity, and discuss the relation to recent experiments. At increasing temperatures the material becomes softer in both the plastic and elastic regime. Porosity in the samples result in a softening of the material; this may be a significant effect in many experiments. ͓S0163-1829͑99͒05941-X͔

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Section: B Reverse Hall-petch Effectmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Atomic-scale simulations of the mechanical deformation of nanocrystalline metals

et al. 1999

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“…1. But, the hardness of as-consolidated nanophase Cu and Pd has k e n shown to increase further with a modest anneal (20); thus, measured hardness variations can be dependent upon the method used to vary the grain size (21). Samples usually exhibit increased hardness with decreasing grain size when individual samples are compared; however, an apparent softening (an artifact) has been observed (22) for samples annealed to increase their grain size.…”

Section: Hardnessmentioning

confidence: 99%

Mechanical properties of nanophase metals

Siegel¹,

Fougere²

1995

Nanostructured Materials

345

120

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“…In addition to softening, a substantial increase (50% or less) in hardness has been reported after annealing some nanocrystalline materials; this has often been attributed to recrystallization of amorphous phases and/or grain boundary relaxation. Figure 8 5,36,[120][121][122][123][124][125][126][127][128][129][130][131][132] plots a number of mechanical properties (hardness, compression, and tension tests) as a function of the inverse grain size (i.e., Hall-Petch relationship, Eq. 1).…”

Section: Yield Stress and Hardnessmentioning

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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Grain-size dependent hardening and softening of nanocrystalline Cu and Pd

Cited by 195 publications

References 8 publications

Atomic-scale simulations of the mechanical deformation of nanocrystalline metals

Atomic-scale simulations of the mechanical deformation of nanocrystalline metals

Mechanical properties of nanophase metals

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

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