On the minimum grain size obtainable by equal channel angular pressing

Mohamed, Farghalli A.; Dheda, Shehreen S.

doi:10.1016/j.msea.2013.04.104

Cited by 26 publications

(12 citation statements)

References 28 publications

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“…An expression was developed for the minimum grain size that may be produced in HPT and inspection shows that this relationship incorporates some features that relate to the initial unprocessed condition such as the dislocation density and the yield stress [39]. A similar approach was also developed later for processing by ECAP [40]. Nevertheless, there is no clear and definitive relationship that specifically dictates the saturation conditions that may be attained after a combination of processing by ECAP and HPT.…”

Section: Discussionmentioning

confidence: 99%

An examination of the saturation microstructures achieved in ultrafine-grained metals processed by high-pressure torsion

Sabbaghianrad

Wongsa-Ngam

Kawasaki

et al. 2014

Journal of Materials Research and Technology

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HardnessHigh-pressure torsion Ultrafine grains a b s t r a c t Experiments were conducted on two commercial alloys, a Cu-0.1%Zr alloy and an Al-7075 aluminum alloy, to investigate the significance of the saturation microstructure which is achieved after processing by high-pressure torsion (HPT). Samples were processed by HPT and also by a combination of equal-channel angular pressing (ECAP) followed by HPT. The results show that the saturation conditions are dependent upon the grain size in the material immediately prior to the HPT processing. Additional grain refinement may be achieved in HPT by initially processing the material to produce an ultrafine-grain size before conducting the processing by HPT.

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Section: Discussionmentioning

confidence: 99%

An examination of the saturation microstructures achieved in ultrafine-grained metals processed by high-pressure torsion

Sabbaghianrad

Wongsa-Ngam

Kawasaki

et al. 2014

Journal of Materials Research and Technology

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“…Recent studies have derived expressions for the minimum grain sizes obtained after processing by HPT or ECAP. Further inspection shows that these relationships incorporate some features related to the initial unprocessed condition such as the dislocation density and the yield stress [40,41]. However, there is no clear and definitive relationship that specifically dictates the saturation conditions that may be attained after a combination of processing by ECAP and HPT.…”

Section: Discussionmentioning

confidence: 99%

Microstructural saturation, hardness stability and superplasticity in ultrafine-grained metals processed by a combination of severe plastic deformation techniques

Sabbaghianrad¹,

Langdon²

2015

LoM

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A commercial Al-7075 aluminum alloy was used to investigate the significance of the saturation hardness and saturation microstructure after processing by high-pressure torsion (HPT) through up to 20 turns or a combination of equal-channel angular pressing (ECAP) for 4 or 8 passes and HPT. The results show additional grain refinement by initially processing the material by ECAP to produce an ultrafine grain size before conducting the HPT. Thus, the grain size immediately prior to the HPT processing controls the saturation microstructure and hardness. Microstructural images reveal a significant grain refinement from elongated grains in the samples prior to processing with an average grain diameter of ~8 μm to equiaxed grains with an average grain size of ~200 nm after processing by a combination of ECAP for 8 passes and HPT through 20 turns. This grain refinement leads to an improvement in the mechanical properties of the Al-7075 alloy. Vickers microhardness tests show a significant increase in the microhardness values of the Al-7075 alloy from Hv≈102 in the annealed samples to Hv≈270 after processing by a combination of ECAP for 8 passes and HPT through 20 turns. Specimens processed by a combination of ECAP and HPT also exhibit excellent superplastic properties with elongations up to >1000% at 673 K.Keywords: aluminum 7075 alloy, equal-channel angular pressing, hardness, high-pressure torsion, severe plastic deformation, superplasticity Насыщение микроструктуры, стабильность твердости и сверхпластичность ультрамелкозернистых металлов, полученных комбинацией методов интенсивной пластической деформацииПромышленный алюминиевый сплав Al-7075 был использован для исследования степени насыщения твердости и насыщения микроструктуры после обработки путем кручения под высоким давлением (КВД) вплоть до 20 оборотов или комбинации равноканального углового прессования (РКУП) в 4 или 8 проходов и КВД. Результаты показывают, что имеет место дополнительное измельчение зерен при предварительной обработке материала путем РКУП, кото-рый создает ультрамелкозернистую структуру перед КВД. Таким образом, размер зерен непосредственно перед КВД определяет микроструктуру и твердость при насыщении. На микроструктурных изображениях выявляется значи-тельное измельчение зерен, их преобразование от удлиненных зерен со средним диаметром около 8 мкм в образцах перед деформацией до равноосных зерен со средним размером около 200 нм после комбинации РКУП в 8 проходов и КВД в 20 оборотов. Это измельчение зерен приводит к улучшению механических свойств сплава Al-7075. Измерения микротвердости по Виккерсу показывают значительное повышение микротвердости сплава Al-7075 от Hv≈102 в отожженных образцах до Hv≈270 после обработки комбинацией РКУП в 8 проходов и КВД в 20 оборотов. Образцы, обработанные комбинацией РКУП и КВД, проявляют также отличные сверхпластические свойства с удлинениями до более чем 1000% при 673 K.

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“…[25] This model was also shown [211] to fit the experimental results of pure fcc and bcc metals studied by Koch, [21] Fecht et al, [46] Fecht [47] and Eckert et al [209] very well, while also cleanly explaining the relationship between d min and parameters such as H, Q, T m , B, milling T, L c , and SFE. Mohamed tested his model against the data for pure fcc and bcc materials processed by HPT, [212] ECAE, [213] and mechanically milled hcp metals [214] and found strong agreement. Lastly, the model was expanded to correlate the smallest grain size achievable with the lattice strain introduced by the mechanical milling; in this case, the (G/r) 1.25 term is replaced by (1/e) 0.94 where e is the lattice strain.…”

Section: ½8mentioning

confidence: 99%

Building on Gleiter: The Foundations and Future of Deformation Processing of Nanocrystalline Metals

Mathaudhu

2020

Metall Mater Trans A

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In 1989, fueled by his prior reports and findings, Prof. Herbert Gleiter published a seminal work on the synthesis, processing, and possibilities for nanocrystalline materials. This spark exploded into the field of bulk nanocrystalline metals by severe plastic deformation processing, with the primary driver being attaining the ultimate strength of a metal through refinement of the grain sizes to a level approaching the theoretically possible limits. This paper will briefly explore the historical development of SPD and based on Turnbull's strategy of ''energizing and quenching'' materials to attain a desirable metastable state, present thoughts on incipient-related areas of exploration, including thermal stabilization through solute additions, the role of trace impurities and interstitials, the smallest grain size achievable (both theoretically and practically), and the captivating yet hazy character and role of the grain boundary. Lastly, some new approaches to making and then controlling the behavior of nanocrystalline materials will be presented. At each stage, opportunities for future study will be raised. On the 50th Anniversary of Metallurgical and Materials Transactions A, it is hoped that this report will build off the seed planted by Gleiter and inspire new work and collaborations in the years to come.

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On the minimum grain size obtainable by equal channel angular pressing

Cited by 26 publications

References 28 publications

An examination of the saturation microstructures achieved in ultrafine-grained metals processed by high-pressure torsion

An examination of the saturation microstructures achieved in ultrafine-grained metals processed by high-pressure torsion

Microstructural saturation, hardness stability and superplasticity in ultrafine-grained metals processed by a combination of severe plastic deformation techniques

Building on Gleiter: The Foundations and Future of Deformation Processing of Nanocrystalline Metals

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