Equal-Channel Angular Pressing and Creep in Ultrafine-Grained Aluminium and Its Alloys

Sklenička, V.; Dvořák, Jiří; Svoboda, Milan; Král, Pétr; Kvapilová, Marie

doi:10.5772/51242

Cited by 13 publications

(13 citation statements)

References 77 publications

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“…As a result, some dislocations in the cell interiors are held up at the interface between cell walls and cell interiors. At the cell interiors, the dislocations are arranged randomly as a three dimensional network structure, which has been confirmed by TEM observation [32].…”

Section: Discussionsupporting

confidence: 55%

See 1 more Smart Citation

Microstructure changes in superplastically deformed ultrafine-grained Al-3Mg-0.2Sc alloy

Král¹,

Dvořák²,

Kvapilová³

et al. 2015

LoM

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Experiments were conducted on an ultrafine-grained Al-3wt.%Mg-0.2wt.%Sc alloy to characterize the microstructure changes occurring during large tensile deformation at elevated temperature within a transition between superplasticity and creep. The coarse-grained material was subjected to equal-channel angular pressing at room temperature using a die which had a 90° angle between the channels. The billets were rotated by 90° in the same sense between each pass in the processing route Bc. The billets were subsequently pressed by 2 and 8 passes. Microstructure was investigated by scanning electron microscope equipped with an electron back scatter diffraction unit. Microstructure analysis showed that the movement of dislocations and the growth of grains were restricted by Al3Sc coherent precipitates formed during stabilizing annealing at 623 K for 1h. It was found that deformation behaviour of investigated Al alloy was influenced by inhomogeneity of microstructure and deformation-induced coarsening of grains. The fracture behaviour was affected by cavity formation due to high local concentration of plastic deformation at the triple points and inefficient accommodation processes of grain boundary sliding. The results showed that total tensile deformation is a consequence of a various mechanisms occurring at different stages of tensile deformation. The superplastic tensile deformation was predominantly realized by grain boundary sliding and formation of mesoscopic shear bands. The role played by grain boundary sliding is discussed.Keywords: ultrafine-grained microstructure, aluminium alloy, equal-channel angular pressing, electron back scatter diffraction Изменения микроструктуры в сверхпластически деформированном ультрамелкозернистом сплаве Al-3Mg-0.2ScПроведены эксперименты на ультрамелкозернистом сплаве Al-3 вес.% Mg-0.2 вес.% Sc с целью выяснения измене-ний микроструктуры, происходящих при большой деформации растяжением при высокой температуре в области перехода между сверхпластичностью и ползучестью. Крупнозернистый материал был подвергнут равноканальному угловому прессованию при комнатной температуре с использованием оснастки, имеющей угол 90° между каналами. В соответствии с маршрутом обработки B c образцы между двумя последовательными переходами поворачивались на угол 90° в одном и том же направлении. Образцы были деформированы путем 2 и 8 проходов. Микроструктура была исследована с помощью сканирующего электронного микроскопа, оборудованного приставкой для дифракции обратно рассеянных электронов. Анализ микроструктуры показал, что движение дислокаций и рост зерен сдер-живаются когерентными включениями Al 3 Sc, образующимися при стабилизирующем отжиге при 623 K в течение 1 ч. Показано, что на деформационное поведение исследованного сплава Al влияет неоднородность микрострук-туры и деформационно-индуцированное укрупнение зерен. На характер разрушения влияет образование пор из-за высокой локальной концентрации пластической деформации около тройных стыков и неэффективная аккомодация процессов зернограничного проск...

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Section: Discussionsupporting

confidence: 55%

“…Finally, the same Al-3Mg-0.2Sc alloy processed by ECAP was creep tested at 473 K using strain rate from 10 -7 to 10 -5 s -1 [32][33][34]. The ultrafine-grained Al-3Mg-0.2Sc alloy exhibited faster creep, by about two to three orders of magnitude, than the unpressed alloy under the same loading conditions.…”

Section: Discussionmentioning

confidence: 99%

Microstructure changes in superplastically deformed ultrafine-grained Al-3Mg-0.2Sc alloy

Král¹,

Dvořák²,

Kvapilová³

et al. 2015

LoM

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“…Instead, the secondary creep stage is reduced to a single point with minimum strain rate particularly for higher loading. Sklenicka et al [7] observed similar results for compression creep tests after ECAP of different aluminum alloys. According to ref., [22] an evolution of the precipitates during creep testing obscures the secondary creep stage.…”

Section: Creep Tests Of Initial Condition and Ecap-deformed Materialsmentioning

confidence: 59%

“…[1] One approach to further improve these properties are processes involving severe plastic deformation (SPD), such as equalchannel angular pressing (ECAP). [2][3][4] The microstructure after SPD processing is often heterogeneous and meta-stable [5][6][7] : the long-term mechanical properties may, therefore, change at elevated temperatures. Moreover, recent studies have highlighted that both creep testing [8] and SPD processes (like ECAP [9,10] or high pressure torsion [5] ) lead to an acceleration of the precipitation kinetics of Al-Cu alloys.…”

Section: Introductionmentioning

confidence: 99%

Effect of Creep and Aging on the Precipitation Kinetics of an Al–Cu Alloy after One Pass of ECAP

et al. 2017

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Recent work shows that severe plastic deformation processes such as ECAP or HPT considerably accelerate the precipitation kinetics of Al-Cu alloys. In this study, the authors analyze how a combination of mechanical load, aging time (and increased plastic strain), and aging temperature affects the precipitation kinetics of an AA2017 alloy after ECAP. After solution annealing, the material is processed by one pass of ECAP (120 -channel angle) at 140 C. Compressive creep tests are performed on the initial condition and the ECAP-deformed material. The resulting microstructures are studied in detail using electron microscopy. To investigate the influence of mechanical loading, interrupted compressive creep tests are performed and compared with aged samples (produced without any mechanical loading at the same temperature and after the same amount of time). By keeping time and load constant in another set of interrupted compressive creep tests, the influence of temperature is investigated. Our study shows that increasing mechanical loading further accelerates the precipitation kinetics. Temperature accelerates the precipitation kinetics as well, but results in coarser precipitates. The authors also find that different creep strains can lead to the formation of two different regions in the microstructure: regions with only a few coarsened uphase precipitates, and regions with numerous, finely dispersed precipitates.

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“…The retention of the same cross-sectional area when processing by ECAE-CE, despite the introduction of very large strains, is the important characteristic of SPD processing and it is characteristic which distinguishes this type of processing from conventional metal-working operations such as rolling, extrusion and drawing. Since the cross-sectional area remains unchanged, the same billet may be pressed repetitively to attain exceptionally high strain (i.e., [1]). …”

Section: Principles Of Ecae-cementioning

confidence: 99%

Finite Element Analysis of Copper Deformed By Conventional Forward Extrusion

Soltantabar¹,

Krishnaiah²,

Tari³

2014

IOSRJMCE

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Equal-Channel Angular Pressing and Creep in Ultrafine-Grained Aluminium and Its Alloys

Cited by 13 publications

References 77 publications

Microstructure changes in superplastically deformed ultrafine-grained Al-3Mg-0.2Sc alloy

Microstructure changes in superplastically deformed ultrafine-grained Al-3Mg-0.2Sc alloy

Effect of Creep and Aging on the Precipitation Kinetics of an Al–Cu Alloy after One Pass of ECAP

Finite Element Analysis of Copper Deformed By Conventional Forward Extrusion

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