The presence and nature of vacancy type defects in nanometals detained by severe plastic deformation

Setman, Daria; Schafler, Erhard; Korznikova, Elena A.; Zehetbauer, M.

doi:10.1016/j.msea.2007.06.093

Cited by 198 publications

(141 citation statements)

References 16 publications

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“…Ta and also for other metals E A,x is substantially lower than the activation energy for self- strongly influenced and aided by a high density of deformation induced defects such as vacancies and dislocations [38,39,82].…”

Section: The Highest Value Of E Ax Obtained Through Fitting Is 19 Kjmentioning

confidence: 97%

“…we assume that if defects other than dislocations or grain boundaries are created, they do not substantially alter predictions. (For discussions on the effect of vacancies see Section 5 and [38,39].) Dislocation annihilation within grains can occur through several mechanisms.…”

Section: Dislocation Generation and Thermally Activated Dislocation Amentioning

confidence: 99%

“…Little is known about E A,x for recovery during HPT. It is expected that E A,x is substantially lower than the activation energy for self-diffusion due to the presence of a high density of defects, which include dislocations and vacancies [38,39]. In addition, it has been established in several works that the activation energy for self-diffusion generally increases linearly with the melting temperature of metals [41,42].…”

Section: Dislocation Generation and Thermally Activated Dislocation Amentioning

confidence: 99%

“…In refinements of the model also a detailed modelling of vacancy concentration and it effect on strength (see eg [39,97]) and dislocation annihilation should be considered.…”

Section: Alternative Models and Mechanismsmentioning

confidence: 99%

See 3 more Smart Citations

Hardening of pure metals by high-pressure torsion: A physically based model employing volume-averaged defect evolutions

2013

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Section: The Highest Value Of E Ax Obtained Through Fitting Is 19 Kjmentioning

confidence: 97%

Section: Dislocation Generation and Thermally Activated Dislocation Amentioning

confidence: 99%

Section: Dislocation Generation and Thermally Activated Dislocation Amentioning

confidence: 99%

“…In refinements of the model also a detailed modelling of vacancy concentration and it effect on strength (see eg [39,97]) and dislocation annihilation should be considered.…”

Section: Alternative Models and Mechanismsmentioning

confidence: 99%

See 2 more Smart Citations

Hardening of pure metals by high-pressure torsion: A physically based model employing volume-averaged defect evolutions

2013

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“…First is lower vacancy density in the CTD sample, related to diffusion affecting microstructure evolution, [30] due to relatively lower pressure and strain than in samples after the HPT process. [31] The second involves relatively stable twin boundaries generated during deformation under conditions of cryogenic temperature, high strain rate, and moderate strain. [10,32] A proper amount of strain (~1.7) and stable twin boundaries, which maintain tolerable misorientations, also suppress the activation of full recrystallization during diffusion-related recrystallization.…”

Section: Resultsmentioning

confidence: 99%

Bi-modal Structure of Copper via Room-Temperature Partial Recrystallization After Cryogenic Dynamic Compression

Ahn

Lee

Kang

et al. 2016

Metall Mater Trans A

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PURE copper was compressed at high strain rates (over~3 9 10 3 s À1 ) under liquid nitrogen. This deformation resulted in bi-modal microstructures of ultrafine grains and abnormally grown micro grains, and in greater hardness (by~30 Hv) than room-temperature, dynamically deformed copper. This bi-modal microstructure is attributable to partial recrystallization at room temperature, activated by high-energy states and by twins generated at high ZenerHollomon parameter conditions. This result demonstrates a new approach for producing bi-modally structured materials.

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Plasticity and Grain Boundary Diffusion at Small Grain Sizes

et al. 2010

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Severe plastic deformation (SPD) processes have attracted considerable attention due to their potential for fabricating large quantities of material with an overall small grain size. [1,2] In the last decade, various SPD processes have been proposed for ultragrain refinement, such as high pressure torsion (HPT), [1] equal channel angular pressing (ECAP) [3] accumulative roll bonding (ARB) [4] or-for achieving the smallest grain sizes for pure metals through SPD-repeated cold rolling (RCR) [5,6] as attractive routes for fabricating bulk nanoand submicron-grained materials. With these approaches, high densities of lattice defects are introduced into the material, which, according to the general view, can then rearrange to attain a minimum energy configuration by forming a submicron cell/sub-grain structure that can evolve to a fine grained microstructure with large fractions of high angle grain boundaries (HAGBs) upon continued straining. It has been observed that materials with fine grain sizes that had been synthesized by such a severe deformation route, exhibit spectacular properties and property combinations, such as, e.g., a very high yield strength and high ductility at the same time, enhanced hydrogen storage capacity and enhanced hydrogen permeation velocity or combinations of high mechanical strength and high electrical conductivity, see, e.g., the recent overview in ref. [7] Along with the modification of the grain structure towards finer grains, the high number of lattice defects that are created led to the postulation of modifications of the grain boundary structure to explain the unusual (mechanical) properties that were observed. In the simplest description, high numberBulk nanostructured-or ultrafine-grained materials are often fabricated by severe plastic deformation to break down the grain size by dislocation accumulation. Underlying the often spectacular property enhancement that forms the basis for a wide range of potential applications is a modification of the volume fraction of the grain boundaries. Yet, along with the property enhancements, several important questions arise concerning the accommodation of external stresses if dislocation-based processes are not longer dominant at small grain sizes. One question concerns so-called ''non-equilibrium'' grain boundaries that have been postulated to form during severe deformation and that might be of importance not only for the property enhancement known already today, but also for spectacular applications in the context of, e.g., gas permeation or fast matter transport for self-repairing structures. This contribution addresses the underlying issues by combining quantitative microstructure analysis at high resolution with grain boundary diffusion measurements.758

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The presence and nature of vacancy type defects in nanometals detained by severe plastic deformation

Cited by 198 publications

References 16 publications

Hardening of pure metals by high-pressure torsion: A physically based model employing volume-averaged defect evolutions

Hardening of pure metals by high-pressure torsion: A physically based model employing volume-averaged defect evolutions

Bi-modal Structure of Copper via Room-Temperature Partial Recrystallization After Cryogenic Dynamic Compression

Plasticity and Grain Boundary Diffusion at Small Grain Sizes

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