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Grain boundary strengthening

About: Grain boundary strengthening is a research topic. Over the lifetime, 8585 publications have been published within this topic receiving 286232 citations.


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Journal ArticleDOI
20 Jan 2011-Nature
TL;DR: This work determines the location and identity of every atom at a grain boundary and finds that different grains stitch together predominantly through pentagon–heptagon pairs, and reveals an unexpectedly small and intricate patchwork of grains connected by tilt boundaries.
Abstract: The properties of polycrystalline materials are often dominated by the size of their grains and by the atomic structure of their grain boundaries. These effects should be especially pronounced in two-dimensional materials, where even a line defect can divide and disrupt a crystal. These issues take on practical significance in graphene, which is a hexagonal, two-dimensional crystal of carbon atoms. Single-atom-thick graphene sheets can now be produced by chemical vapour deposition on scales of up to metres, making their polycrystallinity almost unavoidable. Theoretically, graphene grain boundaries are predicted to have distinct electronic, magnetic, chemical and mechanical properties that strongly depend on their atomic arrangement. Yet because of the five-order-of-magnitude size difference between grains and the atoms at grain boundaries, few experiments have fully explored the graphene grain structure. Here we use a combination of old and new transmission electron microscopy techniques to bridge these length scales. Using atomic-resolution imaging, we determine the location and identity of every atom at a grain boundary and find that different grains stitch together predominantly through pentagon-heptagon pairs. Rather than individually imaging the several billion atoms in each grain, we use diffraction-filtered imaging to rapidly map the location, orientation and shape of several hundred grains and boundaries, where only a handful have been previously reported. The resulting images reveal an unexpectedly small and intricate patchwork of grains connected by tilt boundaries. By correlating grain imaging with scanning probe and transport measurements, we show that these grain boundaries severely weaken the mechanical strength of graphene membranes but do not as drastically alter their electrical properties. These techniques open a new window for studies on the structure, properties and control of grains and grain boundaries in graphene and other two-dimensional materials.

1,824 citations

Journal ArticleDOI
TL;DR: In this article, the average grain size of a log-normal distribution of grain sizes with tetrakaidecahedral shape is related to the average intercept size by a proportionality constant.
Abstract: A model is proposed which realistically characterizes the grain structure of polycrystalline ceramics. The average grain size of a log-normal distribution of grain sizes with tetrakaidecahedral (truncated octahedral) shape is related to the average intercept size by a proportionality constant. This result can be used to determine the average grain size of a sintered powder compact composed of nontextured grains which shows no discontinuous grain growth.

1,732 citations

Journal ArticleDOI
01 Feb 1998-Nature
TL;DR: In this paper, the deformation of nanocrystalline copper has been studied and it is shown that the hardness and yield stress of the material typically increase with decreasing grain size, a phenomenon known as the reverse Hall-Petch effect.
Abstract: Nanocrystalline solids, in which the grain size is in the nanometre range, often have technologically interesting properties such as increased hardness and ductility. Nanocrystalline metals can be produced in several ways, among the most common of which are high-pressure compaction of nanometre-sized clusters and high-energy ball-milling1,2,3,4. The result is a polycrystalline metal with the grains randomly orientated. The hardness and yield stress ofthe material typically increase with decreasing grain size, a phenomenon known as the Hall–Petch effect5,6. Here we present computer simulations of the deformation of nanocrystalline copper, which show a softening with grain size (a reverse Hall–Petch effect3,7) for the smallest sizes. Most of the plastic deformation is due to a large number of small ‘sliding’ events of atomic planes at the grain boundaries, with only a minor part being caused by dislocation activity in the grains; the softening that we see at small grain sizes is therefore due to the larger fraction of atoms at grain boundaries. This softening will ultimately impose a limit on how strong nanocrystalline metals may become.

1,550 citations

Journal ArticleDOI
TL;DR: In this paper, the authors provide an overview of metal-based material classes whose properties as a function of external size have been investigated and provide a critical discussion on the combined effects of intrinsic and extrinsic sizes on the material deformation behavior.

1,515 citations

Journal ArticleDOI
09 Mar 2000-Nature
TL;DR: It is shown that fully dense cubic Y2O3 with a grain size of 60 nm can be prepared by a simple two-step sintering method, at temperatures of about 1,000 °C without applied pressure, and the suppression of the final-stage grain growth is achieved by exploiting the difference in kinetics between grain- boundary diffusion and grain-boundary migration.
Abstract: Sintering is the process whereby interparticle pores in a granular material are eliminated by atomic diffusion driven by capillary forces. It is the preferred manufacturing method for industrial ceramics. The observation of Burke and Coble that certain crystalline granular solids could gain full density and translucency by solid-state sintering was an important milestone for modern technical ceramics. But these final-stage sintering processes are always accompanied by rapid grain growth, because the capillary driving forces for sintering (involving surfaces) and grain growth (involving grain boundaries) are comparable in magnitude, both being proportional to the reciprocal grain size. This has greatly hampered efforts to produce dense materials with nanometre-scale structure (grain size less than 100 nm), leading many researchers to resort to the 'brute force' approach of high-pressure consolidation at elevated temperatures. Here we show that fully dense cubic Y2O3 (melting point, 2,439 degrees C) with a grain size of 60 nm can be prepared by a simple two-step sintering method, at temperatures of about 1,000 degrees C without applied pressure. The suppression of the final-stage grain growth is achieved by exploiting the difference in kinetics between grain-boundary diffusion and grain-boundary migration. Such a process should facilitate the cost-effective preparation of other nanocrystalline materials for practical applications.

1,328 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023103
2022228
2021143
2020124
2019121
2018109