In-situ TEM observation of dynamic interaction between dislocation and cavity in BCC metals in tensile deformation

Tougou, Kouichi; Shikata, Akihito; Kawase, Uchu; Onitsuka, Toshihiro; Fukumoto, Ken-ichi

doi:10.1016/j.jnucmat.2015.05.046

Cited by 14 publications

(3 citation statements)

References 23 publications

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“…Instead of a classical Orowan loop which lies on a plane, this generates a twisted noose around the precipitate, which stays connected to the parent line dislocation for some time. This bears similarity to experimental observations of screw dislocations in BCC materials where they unpin from obstacles by twisting around them, resulting in edge segments on different planes 52 , 53 . At long time scales and high temperatures the noose configuration may relax as the trailing edge segments can move via climb and annihilate each other 54 .…”

Section: Discussionsupporting

confidence: 86%

Effects of precipitates and dislocation loops on the yield stress of irradiated iron

Lehtinen

Laurson

Granberg

et al. 2018

Sci Rep

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Plastic deformation of crystalline materials is governed by the features of stress-driven motion of dislocations. In the case of irradiated steels subject to applied stresses, small dislocation loops as well as precipitates are known to interfere with the dislocation motion, leading to an increased yield stress as compared to pure crystals. We study the combined effect of precipitates and interstitial glissile dislocation loops on the yield stress of iron, using large-scale three-dimensional discrete dislocation dynamics simulations. Precipitates are included in the simulations using our recent multi-scale implementation [A. Lehtinen et al., Phys. Rev. E 93 (2016) 013309], where the strengths and pinning mechanisms of the precipitates are determined from molecular dynamics simulations. In the simulations we observe dislocations overcoming precipitates with an atypical Orowan mechanism which results from pencil-glide of screw segments in iron. Even if the interaction mechanisms with dislocations are quite different, our results suggest that in relative terms, precipitates and loops of similar sizes contribute equally to the yield stress in multi-slip conditions.

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Section: Discussionsupporting

confidence: 86%

Effects of precipitates and dislocation loops on the yield stress of irradiated iron

Lehtinen

Laurson

Granberg

et al. 2018

Sci Rep

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“…Some irradiation effects may be simulated using highly accelerated charged particles (ions), but these affect only a surface layer that is up to a few tens of micrometres deep, at most. This is sufficient to study defect structures and dislocation behaviour 7 8 , but the effects of ion irradiation on mechanical properties must be studied by micromechanical testing 9 10 11 .…”

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confidence: 99%

Quantifying yield behaviour in metals by X-ray nanotomography

Mostafavi

Bradley

Armstrong

et al. 2016

Sci Rep

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Nanoindentation of engineering materials is commonly used to study, at small length scales, the continuum mechanical properties of elastic modulus and yield strength. However, it is difficult to measure strain hardening via nanoindentation. Strain hardening, which describes the increase in strength with plastic deformation, affects fracture toughness and ductility, and is an important engineering material property. The problem is that the load-displacement data of a single nanoindentation do not provide a unique solution for the material’s plastic properties, which can be described by its stress-strain behaviour. Three-dimensional mapping of the displacement field beneath the indentation provides additional information that can overcome this difficulty. We have applied digital volume correlation of X-ray nano-tomographs of a nanoindentation to measure the sub-surface displacement field and so obtain the plastic properties of a nano-structured oxide dispersion strengthened steel. This steel has potential applications in advanced nuclear energy systems, and this novel method could characterise samples where proton irradiation of the surface simulates the effects of fast neutron damage, since facilities do not yet exist that can replicate this damage in bulk materials.

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“…In most cases, slip occurs on {110} and {112} planes. For example, it is {110} in pure Fe at the ambient and low temperature [73,74], both {110} and {112} in pure Mo [75,76], and only {112} for pure V [75]. Occasionally, other slip planes, such as {123} and other crystalline planes with high index {hkl}were also reported [66,73,74,77,78].…”

Section: Dislocation-mediated Plasticity In Bcc Crystalline Structuresmentioning

confidence: 99%

Size effect for achieving high mechanical performance body-centered cubic metals and alloys

2018

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Submicron and nanostructured body-centered cubic (BCC) metals exhibit unusual mechanical performance compared to their bulk coarse-grained counterparts, including high yield strength and outstanding ductility. These properties are important for their applications in micro-, nano-and even atomic-scale devices as well as for their usages as components for enhancing the performances of structural materials. One aspect of the unusual mechanical properties of small-sized BCC metals is closely related to their dimensional confinement. Decreasing the dimensions of single crystalline metals or the grain sizes of polycrystalline metals contributes significantly to the strengthening of the small-sized BCC metals. In the last decade, significant progress has been achieved in understanding the plasticity and deformation behaviors of small-sized BCC metals. This paper aims to provide a comprehensive review on the current understanding of size effects on the plasticity and deformation mechanisms of small-sized BCC metals. The techniques used for in situ characterization of the deformation behavior and mechanical properties of small-sized samples are also presented.

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In-situ TEM observation of dynamic interaction between dislocation and cavity in BCC metals in tensile deformation

Cited by 14 publications

References 23 publications

Effects of precipitates and dislocation loops on the yield stress of irradiated iron

Effects of precipitates and dislocation loops on the yield stress of irradiated iron

Quantifying yield behaviour in metals by X-ray nanotomography

Size effect for achieving high mechanical performance body-centered cubic metals and alloys

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