Influence of ECAP on precipitate distributions in a spray-cast aluminum alloy

Xu, Cheng; Furukawa, Mutsuhisa; Horita, Zenji; Langdon, Terence G.

doi:10.1016/j.actamat.2004.10.026

Cited by 168 publications

(88 citation statements)

References 60 publications

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“…[132] For example, when the spray-cast Al-7034 alloy is processed by ECAP at a temperature of 473 K (200°C) the grain size is reduced from ~2.1 to ~0.3 μm after 6 passes but subsequent tensile testing shows an overall weakening which is attributed to the partial loss during ECAP processing of the hardening metastable η′ phase. [133] An example of this weakening is shown by the results obtained for this alloy in compression testing at room temperature using an initial strain rate of 5.5 × 10 -4 s -1 where the upper curve in Fig. 11 is for the as-received unprocessed alloy and the lower curves are for samples processed through 1, 2 and 6 passes of ECAP: the designation Z direction refers to cutting the samples perpendicular to the flow direction and perpendicular to the upper surface of the ECAP billet.…”

Section: Weakening By Spdmentioning

confidence: 99%

The Strength–Grain Size Relationship in Ultrafine-Grained Metals

Balasubramanian

Langdon

2016

Metall Mater Trans A

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Metals processed by severe plastic deformation [SPD] techniques, such as equal-channel angular pressing [ECAP] and high-pressure torsion [HPT], generally have submicrometer grain sizes. Consequently, they exhibit high strength as expected on the basis of the HallPetch [H-P] relationship. Examples of this behavior are discussed using data on Ti, Al-Mg 1 and Ni. These materials typically have grain size above ~50 nm where softening is not expected. An increase in strength is usually accompanied by a decrease in ductility. High strength and ductility can be achieved simultaneously by imposing high strains to give both ultrafine grain sizes and a high fraction of high-angle grain boundaries. An example is presented for a cast Al-7% Si alloy processed by HPT. In some cases, SPD may produce a fine grain size but also lead to a weakening due to microstructural changes as in ECAP of an Al-7034 alloy and HPT of Zn-22% Al. In SPD-processed materials, grain boundary segregation and nanostructural features are present which may lead to higher strengths than those predicted by the H-P relationship in some alloys having nano grain sizes.

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Section: Weakening By Spdmentioning

confidence: 99%

The Strength–Grain Size Relationship in Ultrafine-Grained Metals

Balasubramanian

Langdon

2016

Metall Mater Trans A

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“…From the similarity of most of these patterns, it is deduced that about 90% of the billet deforms in a very similar manner, with a small region at the edge of the billet that passed through the outer intersections of the channels (encompassing S 5 and S 6 ) showing evidence for a different deformation history. It is important to record also that earlier analyses of the microstructures produced in this alloy by ECAP revealed the formation and subsequent coarsening of small disc-shaped η-phase precipitates [15] and the fragmentation during pressing of the coarse rod-shaped η-phase precipitates [16,17].…”

Section: Resultsmentioning

confidence: 99%

Texture evolution by shear on two planes during ECAP of a high-strength aluminum alloy

et al. 2008

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The evolution of texture was examined during equal-channel angular pressing (ECAP) of an Al-Zn-Mg-Cu alloy having a strong initial texture. An analysis of the local texture using electron back-scatter diffraction demonstrates that shear occurs on two shear planes: the main shear plane (MSP) equivalent to the simple shear plane, and a secondary shear plane which is perpendicular to the MSP. Throughout most regions of the ECAP billet, the MSP is close to the intersection plane of the two channels but with a small (5˚) deviation. Only the {111}<110> and {001}<110> shear systems were activated and there was no experimental evidence for the existence of other shear systems. In a small region at the bottom edge of the billet that passed through the zone of intersection of the channels, the observed textures were fully consistent with the rolling textures of Copper and Goss.

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“…It has been reported that ECAP at ambient temperature suppresses the precipitation in the as quenched condition [10], while ECAP at elevated temperature may cause dissolution of pre-existing metastable precipitates or precipitation in the case of the as quenched alloy [9]. A morphological change has been reported in Al-ZnMg-Cu alloys [15], where spherical precipitates form by fragmentation of pre-existing large platelet precipitates, or by isotropic growth of small platelet precipitates [11].…”

Section: Introductionmentioning

confidence: 99%

Microstructural evolution of AA7050 al alloy processed by ECAP

et al. 2010

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This work aimed to study the microstructural evolution of commercial aluminum alloy AA7050 in the solution treated condition (W) processed by equal channel angular pressing -ECAP. The analyses were made considering the effects of process parameters as temperature (T amb and 150°C), processing route (A and B C ) and number of passes. Optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for microstructural characterization, and hardness tests for a preliminary assessment of mechanical properties. The results show that the refining of the microstructure by ECAP occurred by the formation of deformation bands, with the formation of dislocations cells and subgrains within these bands. The increase of the ECAP temperature led to the formation of more defined subgrains contours and intense precipitation of η phase in the form of spherical particles. The samples processed by Route B C present a more refined microstructure.Keywords: aluminum alloy; ECAP; microstructure. INTRODUCTIONSevere plastic deformation (SPD) techniques have been widely used for the production of ultra fined grained microstructures in metal and alloys [1][2]. Among the various SPD processes available, equal channel angular pressing, ECAP is especially attractive because it is the most cost effective and easiest way due to the simplicity of process and tooling and because it can be scale-up to produce bulk ultra fined grained materials for structural applications. The process allows materials to undergo severe shearing deformation and break up the original texture into ultrafined or nanostructure after a number of passes of pressing through a die composed by two channels that intersect in an angle usually of 90° or 120° [1][2][3][4]. The process imposes a high strain on the sample so that a high dislocation density is introduced. These dislocations re-arrange during the multiple passes of ECAP to form subgrains and subsequently new high angle grain boundaries.Investigation of ECAP processing of precipitation-hardened Al alloys was primary focused on the process refinement [5][6][7][8] and more recently on the evolution and controlling of precipitation microstructure [9][10][11][12][13]. Previous studies [4,14] have reported that different microstructures can be obtained in Al and Al alloys dependent upon the ECAP route. Gholinia et al [5] have demonstrated that during deformation with a constant strain path the grains in the alloy subdivide by the buildup of disorientations between cell blocks as the strain increases. This leads to the formation of elongated subgrains. When a billet is processed with a clockwise and anticlockwise 90° rotation, between each alternate pressing, this results in the continual buildup of shear on two mutually orthogonal planes. This is the less efficient route to produce submicron grains [5]. With a 90° rotation in the same direction, the billet is again sheared in two mutually orthogonal planes, but despite the redundant nature of the total strain, this p...

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Influence of ECAP on precipitate distributions in a spray-cast aluminum alloy

Cited by 168 publications

References 60 publications

The Strength–Grain Size Relationship in Ultrafine-Grained Metals

The Strength–Grain Size Relationship in Ultrafine-Grained Metals

Texture evolution by shear on two planes during ECAP of a high-strength aluminum alloy

Microstructural evolution of AA7050 al alloy processed by ECAP

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