Kinetics and thermodynamics associated with Bi adsorption transitions at Cu and Ni grain boundaries

Tai, Kaiping; Feng, Lin; Dillon, Shen J.

doi:10.1063/1.4805361

Cited by 7 publications

(5 citation statements)

References 48 publications

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“…Measurements of grain boundary diffusivity in Cu-Bi alloys showed an abrupt increase of two orders of magnitude in the diffusivity at relatively low Bi concentrations [25], which was connected to a discontinuity in the slope of the grain boundary energy [55] (i.e., a signal that a complexion transition occurred). Complexion-induced diffusivity transitions were also found observed in Ni-Bi and Cu-Bi by Tai et al [56] using secondary ion mass spectroscopy depth profiling. If grain boundary energy is reduced due to a reduction in enthalpy, one would expect a reduction in diffusivity [57].…”

Section: Thermal Stability Of Nano-grainssupporting

confidence: 57%

“…If grain boundary energy is reduced due to a reduction in enthalpy, one would expect a reduction in diffusivity [57]. Thus, the increase in diffusivity with a transition to a lower energy state signifies that entropy changes may be more important [56]. In any case, accelerated mass transport due to complexion formation at heavily doped boundaries should speed up consolidation or allow consolidation to occur at lower temperatures.…”

Section: Thermal Stability Of Nano-grainsmentioning

confidence: 99%

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The role of complexions in metallic nano-grain stability and deformation

Rupert

2016

Current Opinion in Solid State and Materials Science

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Nanocrystalline metals have excellent strength due to the high density of grain boundaries inside. However, these same boundaries lead to limited thermal stability and a tendency to fail in a brittle manner, issues which limit the practical usage of these materials. Most strategies for stabilization of nano-grains against coarsening rely on the idea of using segregating dopants to lower excess boundary energy. The theory of interface complexions is a useful tool for describing the thermodynamics behind segregation as well as identifying distinct segregation patterns. Some of these same complexions can also dramatically alter mechanical behavior. Unlike past strategies, which always result in a trade-off between strength and ductility, the addition of complexions can potentially increase ductility while retaining or even increasing strength. In this paper, we discuss how complexions offer a unique opportunity to address these limitations simultaneously. In addition to reviewing the current-state-of-the-art, important areas where innovation is needed are also identified.

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Section: Thermal Stability Of Nano-grainssupporting

confidence: 57%

Section: Thermal Stability Of Nano-grainsmentioning

confidence: 99%

The role of complexions in metallic nano-grain stability and deformation

Rupert

2016

Current Opinion in Solid State and Materials Science

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Section: /10mentioning

confidence: 85%

“…This unusual behavior was firstly interpreted as a local disintegration of solids resulted in colloidal disperse systems [4,5]. Later, such approach was supported by the ideas about liquid channels [14,15] and corresponding grain boundary phase transitions [25,26].However, such interpretation of preceded plastic deformation is seriously discredited by a remarkable similarity between LME and hydrogen embrittlement, HE, where local plastic flow always precedes the fracture. Systematic comparative studies of LME and HE were carried out by Lynch [27].…”

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confidence: 99%

On the Nature of Similarity in Embrittlement of Metals by Hydrogen and Surfactants

et al. 2017

MSEIJ

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A mechanism for a similar effect of hydrogen and surface-active elements, surfactants, on the structure and properties of metals is discussed based on studies of austenitic steels and using the ab initio calculations and experimental measurements of the electron structure, mechanical spectroscopy and tension tests. The similarity is originated from the local enhancement of the metallic character of interatomic bonds. The obtained results are interpreted within the frame of the electron approach to the hydrogen-enhanced localized plasticity phenomenon, HELP, in hydrogen embrittlement. The surfactants increase the density of electron states at the Fermi level and, correspondingly, the concentration of free electrons. As a response, a local decrease of the shear modulus resulted in the initiation of dislocation sources, decrease of the line tension of dislocations and distance between their assembles is expected, which facilitates the opening and propagation of cracks and mechanical degradation. The comparison with the adsorption-induced dislocation emission hypothesis, AIDE, for hydrogen and liquid metal embrittlements is carried out. Keywords: On the Nature of Similarity in Embrittlement of Metals by Hydrogen and Surfactants 2/10Copyright: ©2017 Gavriljuk et al.Important for clarification of the operative mechanism was the observation that, including LME, embrittlement by surfactants is accompanied by a local increase of plasticity [22][23][24]. In other words, the locally enhanced plastic deformation precedes the macrobrittle fracture. This unusual behavior was firstly interpreted as a local disintegration of solids resulted in colloidal disperse systems [4,5]. Later, such approach was supported by the ideas about liquid channels [14,15] and corresponding grain boundary phase transitions [25,26].However, such interpretation of preceded plastic deformation is seriously discredited by a remarkable similarity between LME and hydrogen embrittlement, HE, where local plastic flow always precedes the fracture. Systematic comparative studies of LME and HE were carried out by Lynch [27]. Based on these studies, he has proposed the adsorption-induced localized-slip process to be responsible for both the LME and HE phenomena [28] and, correspondingly, developed the hypothesis of adsorption-induced dislocation emission, AIDE [29]. Its main idea amounts to the adsorption of hydrogen and surfactant atoms at the internal crack tips, which facilitates the nucleation and emission of dislocations. Once nucleated, the dislocations can readily move away from the crack tip under applied stress.Along with AIDE hypothesis, hydrogen embrittlement of metals is described by hypotheses of hydrogen-enhanced decohesion, HEDE, hydrogen-enhanced localized plasticity, HELP, and hydrogen-enhanced strain-induced vacancies, HESIV. Their critical analysis is presented, e.g., in the review articles [29,30]. The AIDE and HELP hypotheses seem to be the most acceptable for application to the both HE and LME processes.Probably first time, the ...

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“…In the attempt to interpret this unusual behaviour, the local disintegration of solids resulted in colloidal disperse systems was proposed in [5,6]. Such an approach was complemented by the ideas about liquid channels [15,16] and corresponding grain boundary phase transitions [27,28].…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Embrittlement of Metals by Surface-Active Elements

Teus¹,

Shanina²,

Konchits³

et al. 2018

Metallofiz. Noveishie Tekhnol.

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The nature of mechanical degradation of metals caused by surface-active elements is studied based on the effects of iodine and gallium in austenitic steels and using ab initio calculations and experimental measurements of electronic structure, X-ray diffraction, mechanical spectroscopy, and mechanical tests. A significant increase in the density of electron states at the Fermi level for iodine in f.c.c. iron is shown that is in consistent with the measurements of the increased concentration of free electrons caused by iodine in austenitic steels. Consequently, the increase in mobility of dislocations by iodine and gallium in austenitic steels is revealed. The localization of the enhanced plastic deformation is discussed as a condition for brittleness. The obtained results are at variance with the widely spread opinion about the determining role of surface energy in a liquid-metal brittleness and, instead, are interpreted based on the correlation between atomic interactions and dislocation properties. Applicability of the available HELP and AIDE hypotheses is discussed.Key words: f.c.c. iron, austenitic steel, surfactants, electronic structure, dislocations, mechanical properties.Природу механічної деґрадації металів, яку спричинено дією поверхнево- Ключові слова: ÃЦÊ-çаліçо, аустенітна сталü, сурôактанти, електронна структура, дислокації, механічні властивості.Природа механическоé деградации металлов, обусловленноé поверхност-но-активнûми элементами, бûла иçучена, основûваясü на влиянии éода и галлия на аустенитнûе стали и исполüçуя ab initio-расчётû и эксперимен-талüнûе исследования электронноé структурû, рентгеновскую диôрак-цию, механическую спектроскопию и механические испûтания. Покаçа-но существенное повûøение плотности электроннûх состояниé на уровне Ôерми в случае éода в ÃЦÊ-желеçе, что согласуется с иçмерениями, в ко-торûх бûла çаôиксирована повûøенная концентрация свободнûх элек-тронов, вûçванная éодом в аустенитнûх сталях. Êак следствие, установ-лено повûøение мобилüности дислокациé, вûçванное éодом и галлием в аустенитнûх сталях. Îбсуждается ролü локалиçации повûøенноé пла-стическоé деôормации в качестве условия хрупкости. Полученнûе ре-çулüтатû противоречат øироко распространённому мнению об определя-ющеé роли поверхностноé энергии в жидкометаллическоé хрупкости и, вместо этого, интерпретируются, основûваясü на корреляции между атомнûми вçаимодеéствиями и дислокационнûми своéствами. Îбсужда-ется применимостü гипотеç HELP и AIDE.Ключевые слова: ÃЦÊ-желеçо, аустенитная сталü, сурôактантû, элек-тронная структура, дислокации, механические своéства.

show abstract

Kinetics and thermodynamics associated with Bi adsorption transitions at Cu and Ni grain boundaries

Cited by 7 publications

References 48 publications

The role of complexions in metallic nano-grain stability and deformation

The role of complexions in metallic nano-grain stability and deformation

On the Nature of Similarity in Embrittlement of Metals by Hydrogen and Surfactants

Mechanism of Embrittlement of Metals by Surface-Active Elements

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