Three-dimensional shear-strain patterns induced by high-pressure torsion and their impact on hardness evolution

Cao, Yang; Wang, Y.B.; Figueiredo, Roberto B.; Chang, Li; Liao, Xiaozhou; Kawasaki, Megumi; Wang, Zheng; Ringer, Simon P.; Langdon, Terence G.; Zhu, Yuntian

doi:10.1016/j.actamat.2011.03.015

Cited by 101 publications

(60 citation statements)

References 43 publications

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“…This is consistent with the earlier experimental data reported, e.g. for pure aluminium and aluminium alloys [4,8,[34][35][36][37], high purity copper and copper alloys [13-17, 38, 39], nickel [40,41], steel [42,43], etc.…”

Section: Microstructure and Texture Of The Deformed Statesupporting

confidence: 82%

Tem Study of Recrystallization in Ultra-Fine Grain AA3104 Alloy Processed by High-Pressure Torsion

Paul¹,

Morawiec²,

Baudin³

et al. 2015

Archives of Metallurgy and Materials

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The effect of annealing on the microstructure and the texture development was investigated in a particle containing AA3104 aluminium alloy. The samples were processed at room temperature by high-pressure torsion (HPT) up to ten turns. The nucleation of new grains was analyzed by a transmission electron microscope equipped with a system for local orientation measurements and a heating holder.The shear deformation induces a decrease of the grain size. After the first two turns of the HPT processing the initial structure of large grains was 'transformed' into a structure of fine cells/grains with the diameter of a few tens of nanometers. In the central areas of the samples the elongated shape of the cells/grains was observed up to six turns. For higher deformations, this structural inhomogeneity was totally removed and only the equiaxed grains were observed. The crystal lattice of small grains rotates in such a way that the <111> direction is parallel to the compression axis. After annealing the structure coarsened. Nevertheless, after primary recrystallization, the structure was still composed of relatively fine and equiaxed grains of a similar size. In most of the observed cases the size of the recrystallized grains in the areas close to and far from the large second phase particles was similar. The recrystallization leads to the creation of new texture components. The new grain orientations lost the positions typically observed in the deformed state and showed the tendency for the coincidence of the <100> crystallographic directions with the compression axis.Keywords: High Pressure Torsion, AA3104 alloy, TEM orientation mapping, Texture, Microstructure W pracy analizowano wpływ warunków wyżarzania na zmiany mikrostrukturalne i teksturowe w stopie AA3104 zawierającym wydzielenia cząstek drugiej fazy. Próbki odkształcano z wykorzystaniem techniki skręcania pod wysokim ciśnieniem (HPT), do dziesięciu obrotów, w temperaturze otoczenia. Proces zarodkowania nowych ziaren analizowano z wykorzystaniem transmisyjnej mikroskopii elektronowej wyposażonej w system pomiaru orientacji lokalnych oraz 'heating holder'.Zaobserwowano, że w miarę wzrostu liczby obrotów, intensywne ścinanie prowadzi do silnego zmniejszenia wielkości ziarna. Po dwu obrotach, wyjściowa struktura dużych ziaren uległa przekształceniu w strukturę drobnoziarnistą złożoną z ziaren o wielkości kilkudziesięciu nanometrów. W obszarach próbki zbliżonych do osi obrotu wydłużony kształt ziaren obserwowano do sześciu obrotów. W zakresie wyższych stopni odkształcenia ta niejednorodność strukturalna zanika; obserwowano jedynie równoosiowe ziarna. Orientacja sieci krystalicznej tych ziaren formuje silną teksturę osiową z kierunkiem <111> usytuowanym równolegle do kierunku normalnego (osi ściskania/skręcania). Po wyżarzaniu struktura ulega 'pogrubieniu'. Jednakże, w zakresie rekrystalizacji pierwotnej, w dalszym ciągu pozostaje równoosiowa i silnie rozdrobniona. W większości obserwowanych przypadków wielkość zrekrystalizowanych ziaren w obszarach położonych zarówno ...

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Section: Microstructure and Texture Of The Deformed Statesupporting

confidence: 82%

Tem Study of Recrystallization in Ultra-Fine Grain AA3104 Alloy Processed by High-Pressure Torsion

Paul¹,

Morawiec²,

Baudin³

et al. 2015

Archives of Metallurgy and Materials

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“…Very recently, experiments were conducted on a duplex stainless steel having a two-phase structure, with approximately equal volume fractions of austenitic and ferritic phases, and this provided an opportunity to use optical microscopy to obtain visual displays of the flow patterns produced by the HPT processing. [31][32][33] The results were unexpected because there was evidence for the formation of significant local turbulence including the presence of double-swirl patterns and local shear strain vortices. A possible explanation for these effects may lie in an initial misalignment of the anvils in the HPT facility.…”

mentioning

confidence: 63%

“…[31][32][33] In the present research, inspections showed that local shear vortices were present on some discs but not on others. To clarify the situation, careful observations were made on all discs after HPT processing.…”

Section: Local Flow Patterns Produced By Hpt With Different Anvil Alimentioning

confidence: 89%

Influence of Anvil Alignment on Shearing Patterns in High‐Pressure Torsion

2013

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It is now well established that ultrafine-grain sizes may be produced in bulk metals through the application of severe plastic deformation (SPD). [1] Typical SPD processing techniques include equal-channel angular pressing (ECAP) [2] and high-pressure torsion (HPT) [3] but experimental evidence shows that processing by HPT generally produces ultrafine grains that are smaller than those produced by ECAP. [4][5][6] Accordingly, a significant interest has developed in using HPT processing for the fabrication of metals with submicrometer or nanometer grain sizes.The principles of processing by HPT have been extended recently to the consolidation of metal powders [7,8] and machining chips [9] and the use of HPT in mechanical mixing, [10] investigations of amorphization [11,12] and phase transformations, [13][14][15] evaluations of the hydrogen storage capability of magnesium [16,17] and examinations of structural modifications and the mechanical properties of bulk metallic glasses. [18,19] There is also a very recent demonstration of a continuous high-pressure torsion (CHPT) facility which may be used for the continuous processing of sheets and wires. [20,21] In processing by HPT, the sample is usually in the form of a thin disc, it is held between two massive anvils and it is then subjected to a high compressive pressure, P, and concurrent torsional straining through the rotation of one of the anvils. There are three different types of HPT termed unconstrained HPT, constrained HPT and quasi-constrained HPT, respectively. In unconstrained HPT, the disc is placed between two flat anvils and it is free to flow outwards under the applied pressure. In constrained HPT, the disc is placed within a cavity in the lower anvil so that there is no outward flow when the pressure is applied. In practice, however, most HPT processing is now conducted under quasi-constrained conditions where the disc is placed between depressions in the lower and upper anvils and there is some limited outward flow between the two anvils during the processing operation. [22,23] It has been shown that the experimental results obtained when using HPT depend, at least in part, on the nature of the processing operation. [24,25] In processing by HPT, the equivalent von Mises strain imposed on the disc, e eq , is given by an expression of the form: [26][27][28]

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“…The processing procedures of ECAP and HPT are eective in producing submicrometer arrays of grains or, in some metals, grains within the true nanometer (< 100 nm) range. It was shown through experiments that the grains produced by HPT are generally smaller than those achieved using ECAP [35] and, accordingly, HPT processing is therefore advancing rapidly to become a signicant processing procedure.…”

Section: Introductionmentioning

confidence: 99%

An Evaluation of Homogeneity and Heterogeneity in Metals Processed by High-Pressure Torsion

2012

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Processing through the use of high-pressure torsion is attracting much attention at the present time because of the potential for achieving exceptional grain renement. In principle, it appears that the thin disks used for high-pressure torsion processing should exhibit signicant heterogeneity in the as-processed condition. However, experiments show that the development of homogeneity or heterogeneity is dependent upon the crystalline structure of the material. For high-purity aluminum the as-processed microstructure is very homogeneous after ve or more revolutions of torsional straining but for the magnesium AZ31 alloy there is a considerable degree of heterogeneity in the as-processed disks.

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Three-dimensional shear-strain patterns induced by high-pressure torsion and their impact on hardness evolution

Cited by 101 publications

References 43 publications

Tem Study of Recrystallization in Ultra-Fine Grain AA3104 Alloy Processed by High-Pressure Torsion

Tem Study of Recrystallization in Ultra-Fine Grain AA3104 Alloy Processed by High-Pressure Torsion

Influence of Anvil Alignment on Shearing Patterns in High‐Pressure Torsion

An Evaluation of Homogeneity and Heterogeneity in Metals Processed by High-Pressure Torsion

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