On the validity of the hall-petch relationship in nanocrystalline materials

Chokshi, Atul H.; Rosen, A.; Karch, J.; Gleiter, H.

doi:10.1016/0036-9748(89)90342-6

Cited by 1,108 publications

(481 citation statements)

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“…On the other hand, the yield stress increases with the decreasing grain size, which can be expressed by the well-known Hall-Petch relation [35,36]. In nanoscale regime, this relation has been confirmed by experimental data [37][38][39]. According to the Hall-Petch relation, nanocrystalline materials would display great yield stress as the grain size is reduced to nanometer dimension.…”

Section: Resultsmentioning

confidence: 80%

The uniaxial tensile deformation of Ni nanowire: atomic-scale computer simulations

Zhu

Shao

et al. 2005

Physica E: Low-dimensional Systems and Nanostructures

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The mechanical deformations of nickel nanowire subjected to uniaxial tensile strain at 300 K are simulated by using molecular dynamics with the quantum corrected Sutten-Chen many-body force field. We have used common neighbor analysis method to investigate the structural evolution of Ni nanowire during the elongation process. For the strain rate of 0.1%/ps, the elastic limit is up to about 11% strain with the yield stress of 8.6 GPa. At the elastic stage, the deformation is carried mainly through the uniform elongation of the distances between the layers (perpendicular to the Z-axis) while the atomic structure remains basically unchanged. With further strain, the slips in the {1 1 1} planes start to take place in order to accommodate the applied strain to carry the deformation partially, and subsequently the neck forms. The atomic rearrangements in the neck region result in a zigzag change in the stress-strain curve; the atomic structures beyond the region, however, have no significant changes. With the strain close to the point of the breaking, we observe the formation of a one-atom thick necklace in Ni nanowire. The strain rates have no significant effect on the deformation mechanism, but have some influence on the yield stress, the elastic limit, and the fracture strain of the nanowire. r

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Section: Resultsmentioning

confidence: 80%

The uniaxial tensile deformation of Ni nanowire: atomic-scale computer simulations

Zhu

Shao

et al. 2005

Physica E: Low-dimensional Systems and Nanostructures

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“…By contrast, the lower curve 1 corresponds to the conventional H-P relationship with the advent of a negative slope or a softening behavior at very small grain sizes. [146,147] Some experimental evidence is now available for the positive slope at very small grain sizes [148] and generally the strengthening is attributed to the presence of significant grain boundary segregation at grain sizes smaller than ~100 nm. [149,150] This is an area requiring further investigation but generally it is reasonable to anticipate SPD materials will exhibit improved strength and improved functional properties associated not only with their ultrafine grains but also with other nanostructural features that are not generally available in conventional coarse-grained materials.…”

Section: Superstrength By Spdmentioning

confidence: 99%

The Strength–Grain Size Relationship in Ultrafine-Grained Metals

Balasubramanian

Langdon

2016

Metall Mater Trans A

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Metals processed by severe plastic deformation [SPD] techniques, such as equal-channel angular pressing [ECAP] and high-pressure torsion [HPT], generally have submicrometer grain sizes. Consequently, they exhibit high strength as expected on the basis of the HallPetch [H-P] relationship. Examples of this behavior are discussed using data on Ti, Al-Mg 1 and Ni. These materials typically have grain size above ~50 nm where softening is not expected. An increase in strength is usually accompanied by a decrease in ductility. High strength and ductility can be achieved simultaneously by imposing high strains to give both ultrafine grain sizes and a high fraction of high-angle grain boundaries. An example is presented for a cast Al-7% Si alloy processed by HPT. In some cases, SPD may produce a fine grain size but also lead to a weakening due to microstructural changes as in ECAP of an Al-7034 alloy and HPT of Zn-22% Al. In SPD-processed materials, grain boundary segregation and nanostructural features are present which may lead to higher strengths than those predicted by the H-P relationship in some alloys having nano grain sizes.

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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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On the validity of the hall-petch relationship in nanocrystalline materials

Cited by 1,108 publications

References 5 publications

The uniaxial tensile deformation of Ni nanowire: atomic-scale computer simulations

The uniaxial tensile deformation of Ni nanowire: atomic-scale computer simulations

The Strength–Grain Size Relationship in Ultrafine-Grained Metals

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

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