Influence of particle dispersions on the high-temperature strength of ferritic alloys

Hoelzer, David T.; Bentley, J.; Sokolov, Mikhail A.; Miller, M.K.; Odette, G.R.; Alinger, M.J.

doi:10.1016/j.jnucmat.2007.03.151

Cited by 239 publications

(146 citation statements)

References 11 publications

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“…Such sizes are difficult to produce experimentally ® the smallest particles observed to date appear to be the ³2 nm nanoclusters seen in 14YWT steels. 36) Also, if the particle size becomes too small, Zener pinning may not be effective at elevated temperatures because thermal activation may assist the unpinning of grain boundaries. In contrast to molybdenum and zinc, the critical sizes for aluminum, i.e., a dispersoid size of 34 nm and a Zener grain size of 0.6 µm, are within easy reach of experiments.…”

Section: Critical Dispersoid Sizes and Critical Zener Grainmentioning

confidence: 99%

Hall–Petch Breakdown at Elevated Temperatures

Schneibel¹,

Heilmaier

2014

Mater. Trans.

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The HallPetch effect responsible for the strength of fine-grained and ultrafine-grained (UFG) metals is almost exclusively measured at room temperature. One reason for this is that at elevated temperatures grains tend to coarsen, and this negates the strengthening. The grains may, however, be stabilized by small volume fractions of fine dispersoids. These dispersoids cause direct Orowan strengthening and, by stabilizing the so-called Zener grain size, indirect strengthening due to HallPetch. We show that for most metals the critical Zener grain size above which HallPetch strengthening is more important than Orowan strengthening is lower than, and sometimes even considerably lower than 1 µm, i.e., in the range of UFG metals. Breakdown of the HallPetch relationship, which occurs at elevated temperatures once mechanisms weaker than Hall Petch start to control the strength, is best studied for grain sizes well above this critical grain size. The HallPetch breakdown due to either Coble creep or grain size-dependent dislocation creep is modeled. We present model calculations for copper and verify our approach by comparing with experimental results for ferritic steels containing nanoscale dispersions.

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Section: Critical Dispersoid Sizes and Critical Zener Grainmentioning

confidence: 99%

Hall–Petch Breakdown at Elevated Temperatures

Schneibel¹,

Heilmaier

2014

Mater. Trans.

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“…F or high-temperature applications, polycrystalline grains can be detrimental in structural materials, such as Ni-based superalloys, but they are beneficial for creep-resistant nanostructured ferritic alloys (NFAs) [1][2][3] . The ultrafine grains in NFAs remain unusually stable with little or no grain growth, coarsening or recrystallization up to 800-900°C.…”

mentioning

confidence: 99%

“…The ultrafine grains in NFAs remain unusually stable with little or no grain growth, coarsening or recrystallization up to 800-900°C. Although nanoclusters (NCs) and precipitates that are embedded in the grains and along the grain boundaries 4,5 , together with solute segregation of W and Cr to the grain boundaries, are widely recognized to account for the excellent creep resistance 2,4,[6][7][8] , the ultrafine ferrite grains are also essential in promoting the mechanical strength, for example, via Hall-Petch hardening 9 . Thus, it is important to understand how the ferrite grains deform in response to stresses, particularly, at elevated temperatures.…”

mentioning

confidence: 99%

Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy

Stoica

Miller

et al. 2014

Nat Commun

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Nanostructured ferritic alloys are a new class of ultrafine-grained oxide dispersionstrengthened steels that have promising properties for service in extreme environments in future nuclear reactors. This is due to the remarkable stability of their complex microstructures containing numerous Y-Ti-O nanoclusters within grains and along grain boundaries. Although nanoclusters account primarily for the exceptional resistance to irradiation damage and high-temperature creep, little is known about the mechanical roles of the polycrystalline grains that constitute the ferritic matrix. Here we report an in situ mesoscale characterization of anisotropic responses of ultrafine ferrite grains to stresses using state-ofthe-art neutron diffraction. We show the experimental determination of single-crystal elastic constants for a 14YWT alloy, and reveal a strong temperature-dependent elastic anisotropy that leads to elastic softening and instability of the ferrite. We also demonstrate, from anisotropy-induced intergranular strains, that a deformation crossover exists from lowtemperature lattice hardening to high-temperature lattice softening in response to extensive plastic deformation.

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“…Much higher patterning temperatures are experimentally obtained by using highly NFAs are distinguished from more traditional oxide dispersion steels by a higher number density and smaller size of precipitates, which produce much greater interfacial area available for trapping and recombining point defects [45,[47][48][49][50].…”

Section: Stable Microstructuresmentioning

confidence: 99%

“…These alloys have indeed demonstrated outstanding high temperature properties and remarkable tolerance to irradiation-induced displacement damage [45,[49][50][51].…”

Section: Stable Microstructuresmentioning

confidence: 99%

Atomic-scale design of radiation-tolerant nanocomposites

2010

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Recent work indicates that materials with nanoscale architectures, such as nanolayered Cu-Nb composites and nanoscale oxide dispersion-strengthened steels, are both thermally stable and offer improved performance under irradiation.Current understanding of the atomic-level response of such materials to radiation yields insights into how controlling composition, morphology and interface-defect interactions may further enable atomic-scale design of radiation tolerant nanostructured composite materials. With greater understanding of irradiationassisted degradation mechanisms, this bottom-up design approach may pave the way for creating the extreme environment-tolerant structural materials needed to meet the world's clean energy demand by expanding use of advanced fission and future fusion power.2

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Influence of particle dispersions on the high-temperature strength of ferritic alloys

Cited by 239 publications

References 11 publications

Hall–Petch Breakdown at Elevated Temperatures

Hall–Petch Breakdown at Elevated Temperatures

Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy

Atomic-scale design of radiation-tolerant nanocomposites

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Influence of particle dispersions on the high-temperature strength of ferritic alloys

Cited by 239 publications

References 11 publications

Hall&ndash;Petch Breakdown at Elevated Temperatures

Hall&ndash;Petch Breakdown at Elevated Temperatures

Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy

Atomic-scale design of radiation-tolerant nanocomposites

Contact Info

Product

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Hall–Petch Breakdown at Elevated Temperatures

Hall–Petch Breakdown at Elevated Temperatures