Creep in nanocrystalline zirconia

Ghosh, Santonu

doi:10.1016/j.scriptamat.2014.04.014

Cited by 15 publications

(14 citation statements)

References 37 publications

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“…Using AFM to determine the role of GBS in samples deformed to high strains Most of the earlier studies examined the role of GBS by using AFM in the contact mode to evaluate the surface profile after testing [29,30,[41][42][43][44][45][46]. As also performed in this study, the vertical components of the sliding vector, hvi, were then calculated by subtracting the topographic profiles measured before and after tensile or compressive deformation.…”

Section: Discussionmentioning

confidence: 99%

“…As also performed in this study, the vertical components of the sliding vector, hvi, were then calculated by subtracting the topographic profiles measured before and after tensile or compressive deformation. These earlier studies used one of two approaches to calculate hvi by measuring either (1) the topographic profile over the same set of grains [42,45] or (2) the topographic profile over similar but different sets of grains [29,30,41,43,44,46]. The first method is direct and also provides information on grain rotation and cavity nucleation and growth.…”

Section: Discussionmentioning

confidence: 99%

“…However, this marker line method is not easily adapted for use with UFG metals because the grain sizes are generally of the same order as the widths of the lines and this leads to ambiguities in determining the magnitudes of GBS. Alternative procedures are now available and these include surface profiling using an atomic force microscope (AFM) [29,30,[41][42][43][44][45][46], crosssectional examination in a scanning electron microscope (SEM) after preparation with a focused ion beam [36,37], and orientation imaging microscopy (OIM) conducted in situ within an SEM [47]. For both the AFM and OIM techniques, the sample surface is initially carefully polished and then examined after tensile or compressive testing in order to determine any differences that are introduced due to the deformation.…”

Section: Measuring Gbs In Ufg Metalsmentioning

confidence: 99%

“…The use of AFM has been successful in measuring the contributions of GBS in several investigations [29,30,[41][42][43][44][45] including grains as small as *50 nm [46]. Nevertheless, in all investigations involving AFM, especially when the material was not processed through SPD, the grain boundaries after small amounts of deformation, usually in the range from *10 to 20 %, were clearly discernible and therefore the height profiles provided direct information on the sliding offsets.…”

Section: Measuring Gbs In Ufg Metalsmentioning

confidence: 99%

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The contribution of grain boundary sliding in tensile deformation of an ultrafine-grained aluminum alloy having high strength and high ductility

et al. 2015

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An as-cast Al-7 % Si alloy was processed by high-pressure torsion (HPT) for up to 10 turns at temperatures of 298 or 445 K. The HPT-processed samples had ultrafine-grained structures and they were tested in tension at room temperature at various strain rates in the range from 1.0 9 10 -4 to 1.0 9 10 -2 s -1 . The contributions of grain boundary sliding (GBS) to the total strain were measured directly using atomic force microscopy. Samples simultaneously showing both high strength and high ductility contained the highest fractions of high-angle grain boundaries (HAGB) and exhibited the highest contributions from GBS, whereas samples showing high strength but low ductility gave negligible values for the sliding contributions. It is concluded that high strength and high ductility require both an ultrafine grain size and a high fraction of HAGB.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Measuring Gbs In Ufg Metalsmentioning

confidence: 99%

Section: Measuring Gbs In Ufg Metalsmentioning

confidence: 99%

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The contribution of grain boundary sliding in tensile deformation of an ultrafine-grained aluminum alloy having high strength and high ductility

et al. 2015

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“…11 Schematic illustrations in isometric and side and top views showing the configurations of two neighboring grains, 1 and 2, a before and b after GBS in response to an applied axial stress: the bold lines represent marker lines drawn parallel to the applied stress which incur sharp offsets at grain boundaries equal to v i and w i on the side and top surfaces, respectively, due to the occurrence of GBS [62] at the grain boundaries. In practice, it is feasible to use AFM or SEM to measure v j with the high accuracy that is needed in order to measure the very small offsets in NC and UFG materials [62,67,69,[71][72][73].…”

Section: Effect Of a Short-term Anneal After Processingmentioning

confidence: 99%

Review: Overcoming the paradox of strength and ductility in ultrafine-grained materials at low temperatures

2015

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Ultrafine-grained (UFG) materials with grain sizes in the submicrometer or nanometer range may be prepared through the application of severe plastic deformation (SPD) to bulk coarse-grained solids. These materials generally exhibit high strength but only very limited ductility in low-temperature testing, thereby giving rise to the so-called paradox of strength and ductility. This paradox is examined and a new quantitative diagram is presented which permits the easy insertion of experimental data. It is shown that relatively simple procedures are available for achieving both high strength and high ductility in UFG materials including processing the material to a very high strain and/or applying a very short-term anneal immediately after the SPD processing. Significant evidence is now available demonstrating the occurrence of grain boundary sliding in these materials at low temperatures, where this is attributed to the presence of non-equilibrium grain boundaries and the occurrence of enhanced diffusion along these boundaries.

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Grain Boundary Processes in Strengthening, Weakening, and Superplasticity

Chokshi

2019

Adv Eng Mater

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Grain boundaries provide strength to materials at low temperatures by impeding slip transfer and they weaken materials at high temperatures by intergranular creep processes such as grain boundary sliding (GBS) and diffusion creep. At very fine nanocrystalline grain sizes of <10 nm, it is possible to observe grain boundary weakening rather than strengthening at room temperature. Superplastic flow is observed in a wide range of materials, but the common phenomenology of a high strain rate sensitivity and extensive GBS may arise from varying importance of GBS accommodated by dislocations, diffusion creep, and interface‐controlled diffusion creep. Thus, superplasticity in metals and ceramics involves GBS with dislocation accommodation and interface‐controlled diffusion creep, respectively. It is recognized that grains retain their equiaxed shapes during diffusion creep by grain switching and grain growth. Ultrafine‐grained and nanocrystalline materials with a high strain rate sensitivity of >0.3 deform with a large GBS contribution to total strain of ≈40–80%. There are a limited number of studies showing superplasticity in fine‐grained high‐entropy alloys, involving GBS accommodated by dislocations.

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Creep in nanocrystalline zirconia

Cited by 15 publications

References 37 publications

The contribution of grain boundary sliding in tensile deformation of an ultrafine-grained aluminum alloy having high strength and high ductility

The contribution of grain boundary sliding in tensile deformation of an ultrafine-grained aluminum alloy having high strength and high ductility

Review: Overcoming the paradox of strength and ductility in ultrafine-grained materials at low temperatures

Grain Boundary Processes in Strengthening, Weakening, and Superplasticity

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