Anisotropy in flow and microstructural evolution during superplastic deformation of a layered-microstructured AA8090 Al–Li alloy
25 May 2003-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing (Elsevier)-Vol. 349, Iss: 1, pp 166-182
TL;DR: In this article, the superplastic forming grade sheets of AA8090 Al-Li alloy were observed to contain layers of different microstructure and microtexture across their cross-section along the normal to the rolling direction (RD).
Abstract: The superplastic forming grade sheets of AA8090 Al–Li alloy were observed to contain layers of different microstructure and microtexture across their cross-section along the normal to the rolling direction (RD). The surface layer (SL) material contained coarse equiaxed grains and the dominance of S {1 2 3}[6 3 4] texture whereas the center layer (CL) material contained fine elongated grains and the dominance of Bs {1 1 0}[1 1 2] texture. Tensile specimens, machined to represent the SL of 0.6 mm thickness from the surface towards center (SL), the CL of 0.6 mm thickness, obtained by removing the material of 0.6 mm thickness from each surface towards center (CL), and full thickness (FL) material of 1.8 mm thick, in a sheet of AA8090 Al–Li alloy, were deformed at optimum superplastic condition of strain rate=1×10 −3 s −1 and temperature=803 K to investigate the effect of loading direction. In SL material, the specimen parallel to RD exhibited maximum and the specimen perpendicular to RD exhibited minimum flow stresses. This trend was reversed in CL material. The anisotropy in flow stress could be explained on the basis of texture in the SL material, but the contribution of grain directionality became important in the CL material. The flow behavior of FL material was found to consist of the composite-like contributions of SL and CL materials.
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TL;DR: In this article, the effect of tensile deformation at 530°C at a constant strain rate of 5 × 10−4 −1 on the microstructure, texture and mechanical characteristics of the central layer of commercially processed superplastic Al-Li alloy (AA8090) sheet has been investigated.
43 citations
TL;DR: In this article, the microstructural and crystallographic features of the sliding friction treatment (SFT) induced surface deformation layer in a 7050 aluminum alloy were analyzed using transmission electron microscopy (TEM) and high angle angular dark field scanning TEM (HAADF-STEM) observations.
28 citations
TL;DR: In this article, the mechanical properties and microstructures of the extruded 2196 Al-Cu-Li alloy plates under different heat treatment parameters are tested and characterized along different directions, and it is found that the mechanical property anisotropy of 2196 al-Li Alloy is significantly affected by heat treatment.
26 citations
TL;DR: In this article, the microstructural evolution of banded 5A90 Al-Li alloy during superplastic deformation at 475 °C with an initial strain rate of 8×10−4 s−1 was studied using EBSD technique.
18 citations
23 Feb 2021-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the superplastic deformation behaviors and the evolution processes of the microstructures of an Al-Mg-Li alloy with initial banded grains were studied by means of SEM, EBSD, TEM and FIB techniques.
Abstract: The superplastic deformation behaviors and the evolution processes of the microstructures of an Al–Mg–Li alloy with initial banded grains were studied by means of SEM, EBSD, TEM and FIB techniques. Furthermore, the contribution of GBS and IDS of true strain from 0.21 to 0.74 was quantitatively calculated. The results showed that during the stretching process, the initial banded grains were transformed into equiaxed grains, accompanied by dynamic recrystallization. Dynamic recrystallization refined the grain size, increased the high-angle grain boundaries and reduced the texture. The true stress-strain curve showed work hardening and strain softening. At the initial stage of superplastic deformation, dislocations accumulated obviously, which counteracted the softening effect caused by dynamic recrystallization. Moreover, in this stage, the IDS was the dominant deformation mechanism, with a maximum contribution of 62.3%. In the strain softening stage, the change of m value showed that GBS was the dominant deformation mechanism, and DC and IDS were accommodation mechanisms.
18 citations
References
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TL;DR: In this paper, a general relationship between stress and plastic strain in polycrystalline aggregate is derived for any metal in which individual crystals deform by slipping over preferred planes under a critical shear stress.
Abstract: Summary A general relationship between stress and plastic strain in a polycrystalline aggregate is derived for any metal in which individual crystals deform by slipping over preferred planes under a critical shear stress. Full account is taken of the non-uniform distortion due to mutual constraints between the grains of an aggregate. It is shown that a plastic potential exists which is identical with the yield function. Upper and lower bounds are obtained for an approximate calculation of this function for any applied system of combined stresses.
1,251 citations
TL;DR: In this paper, it was shown that the work-hardness of an isotropic aggregate of face-centred cubic crystals is a function only of the total plastic work if the grains hardened equally.
Abstract: Summary In continuation of a previous paper (Bishop and Hill 1951) it is conjectured that the work done in plastically deforming a polycrystal is approximately equal to that which would be done if the grains were free to deform equally. In conjunction with the principle of maximum plastic work, this enables the yield function of an aggregate to be calculated. This is done for an isotropic aggregate of face-centred cubic crystals, following a determination of the stresses needed to produce multi-slip. The theoretical yield criterion lies between those of Tresca and von Mises, in good agreement with observaton for copper and aluminum. It is shown further that the work-hardening of an aggregate would be a function only of the total plastic work if the grains hardened equally ; the departure from this functional relation is expressed explicitly in terms of the non-uniform hardening.
702 citations
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01 Jan 1985
TL;DR: In this article, Wenk et al. describe the symmetry of pole figures and textures and their relationship to the texture of the textured surfaces of a porphyrias.
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598 citations
TL;DR: The importance attached to the development of aluminum-lithium based alloys may be deduced from the fact that over the past seven years four major international conferences (1-4) have been devoted to these materials: The first was held at Stone Mountain, Georgia, in 1980 (1), and the most recent was in Paris in 1987 (4) as discussed by the authors.
Abstract: The importance attached to the development of aluminum-lithium based alloys may be deduced from the fact that over the past seven years four major international conferences (1-4) have been devoted to these materials: The first was held at Stone Mountain, Georgia, in 1980 (1), and the most recent was in Paris in 1987 (4). This rapid sequence of conferences reflects intense research and devel opment activity within the laboratories of the aerospace companies, the aluminum companies, many universities, research institutes, and govern ment research establishments. One reason for this activity was the need for more fuel efficient aircraft because of escalating fuel prices during the 1970s: the addition of lithium to aluminum simultaneously reduces the density and increases the elastic modulus of the resultant alloy. A second and continuing impetus for the development of these materials comes from the requirements of military aircraft.
294 citations
TL;DR: In this paper, the subgrain growth kinetics of a high purity Al-0.05% Si single-phase aluminium alloy were investigated at room temperature and 350°C.
188 citations