Formation Of Shear Texture Research Articles

Microstructure and texture evolution of friction stir lap welded dissimilar multi‑aluminum stack

This work investigates the microstructural evolution of a dissimilar multiple‑aluminum alloy stack (AA7055, AA7055, AA6022) produced by friction stir lap welding (FSLW). A through-thickness analyses of grain orientation map, grain size and distribution, strain distribution, and texture evolution by electron backscattered diffraction-based characterization technique were performed. Two different welding parameters (combination of tool rotation and traverse speed) were used to study the effects of the welding parameters on these microstructural characteristics. The study shows that higher welding speed and higher rotation speed of the FSLW tool yield finer grains. FSLW resulted in shear texture formation in the weld regions due to high welding speeds. This texture development in the nugget zone is consistent with shear deformation, and (111) pole figures show ideal shear texture components. The Stir Zone (SZ) exhibits shear texture (A/A ̅ and B/B ̅ components), consistent with other shear-assisted processes. Recrystallization mechanisms observed are CDRX in SZ and DDRX in TMAZ (Thermo-Mechanically Affected Zone). Interface analysis reveals the presence of oxide layers between different aluminum sheets, affecting joint mechanical performance. The mechanical property of the lap welded joints was presented in terms of microhardness distribution across the weld cross section. Slightly higher hardness in higher speed welding setup was observed throughout the SZ and AA6022 layer, indicating greater grain refinement and uniform grain structure distribution.

Unveiling slip/nanotwin/nano shear band deformation mechanisms at the copper side in a roll-welded aluminum/copper couple

In this study, the co-deformation behavior of Cu in an Al-Cu couple was evaluated. It is observed that slip, twinning, and partial shear banding were responsible for deformation in Cu during cold welding. For characterization purposes, transmission electron microscopy (TEM) was employed to detect deformation mechanisms after the rolling. It was demonstrated that the formation of nanotwins could have evidently influenced the microstructure of the Cu side. The junction of twin/twin, twin/slip, and twin/shear bands was another major observation and confirmed complex microstructure during rolling. Also, the resulting co-deformation has a noticeable effect on microhardness as compared to the aluminum side. Moreover, the textural investigations were conducted by the X-ray diffraction (XRD) and electron back-scattered diffraction (EBSD) methods after rolling. Textural investigations exhibited a transition from Cube to rolling texture (mainly Brass) and shear (Rotated Cube) textures. For validation of shear deformation texture in Al-Cu, a finite element method (FEM) was employed, and approved experimental textural studies regarding shear texture formation.

Evolution of microstructure, texture, and mechanical properties in a twin-roll cast AA6016 sheet after asymmetric rolling with various velocity ratios between top and bottom rolls

In this paper, we report the evolution of microstructure, texture, and mechanical properties of an AA6016 sheet prepared by twin-roll casting and subsequent asymmetric rolling (ASR). By controlling the velocity ratio (VR) of upper and lower rollers, it is determined that a strong shear strain is induced along the sheet thickness during the ASR process, which results in the formation of shear texture with a {111}//normal direction (ND). When the deformation sheets are annealed at 330 °C, the number and size of grain nuclei are increased with an increase in VR after partial recrystallization. When the sheets are completely recrystallized, different recrystallization mechanisms in symmetrically rolled (SR) and ASR sheets can be determined. The main recrystallization mechanism of the SR sheet is characterized as discontinuous recrystallization (DRX), while continuous recrystallization (CRX) contributes to the development of recrystallization in the ASR sheet, which is accompanied by the formation of finer-grain-band/ultrafine grains. Moreover, compared to that of annealed SR sheets, the shear texture ({111}//ND) of the annealed ASR sheet is enhanced during the nucleation and grain growth of recrystallization while the cube texture weakens, which results in a distinct increase in the Lankford coefficient for the annealed ASR sheet.

Microstructure and Crystallographic Texture of Silicon Iron Modified by Torsion Under Quasihydrostatic Pressure

The electron backscatter diffraction, X-ray diffraction analysis, electromotive force instantaneous measurement, microhardness and coercive force measurement techniques are used to explore the development of the microstructure, crystallographic texture and physico-mechanical properties of silicon iron (Fe-3% Si) alloy under quasi-hydrostatic pressure in a Bridgman anvil. It is found that the alloy deformation is accompanied by its significant hardening. In-plane torsion test shows that the average grain size rapidly decreases down to 185 nm after a quater turn of the movable anvil. With the number of turns increased up to six the grain size gradually decreases down to 150 nm. At the same time, the average size of subgrains is less dependent on the deformation degree. The crystallographic texture evolution involves the formation of the strong {001} texture component after comparatively small megaplastic deformation followed by the simple shear texture formation. Such a behavior can be correctly described in terms of non-equilibrium thermodynamics.

Texture Evolution in an Al-Cu-Mg Alloy During Hot Rolling

The texture evolution in the intermediate (the 1/4 thickness) layer of hot-rolled Al-Cu-Mg alloy sheets was investigated by the x-ray diffraction technique, electron backscattered diffraction analysis and transmission electron microscopy observation. The results showed that a texture transition from the shear texture {001} to the β-fiber textures occurred as the rolling temperature increased to 420 °C. The shear strain caused by friction resulted in this strong shear texture formation at the low rolling temperature. As the rolling temperature increased, the plane strain substituting the shear strain dominated in the intermediate layer, giving rise to a significant increase in the β-fiber textures. Increasing the rolling temperature was found to preferentially activate the non-octahedral {112} slip system, thereby benefiting the development of strong Brass. At the low rolling reduction of 74%, the textures with low intensity tended to converge on the α-fiber, containing Goss, Brass, P and L components. As the rolling reduction increased to 90%, the textures were strengthened and gradually flew toward the β-fiber, containing Brass, Copper and S components. The S and Copper bands were found to be the preferential sites for the development of recrystallizing Cube grains during hot rolling.

Microstructure, texture and mechanical properties during refill friction stir spot welding of 6061-T6 alloy

The evolution of microstructure, texture and mechanical properties during refill friction stir spot welding (RFSSW) of 6061-T6 alloy was investigated in the present paper. The Electron backscattering diffraction results revealed that a significant volume of A/-A, and B/-B component of shear textures was formed in the weld. The sleeve inner wall governed the formation of shear texture beneath the sleeve and pin. Whereas, the shear texture at the sleeve periphery was associated with the material flow when material was discharged from the bottom of the thread on the rotating sleeve. The microstructure evolution in the RFSSW of 6061-T6 alloy was dominated by continue recrystallization. However, the grain boundary bulging and presence of cube texture indicated that the discontinue recrystallization also participate in the grain evolution. The tensile shear strength had a negative correlation with the hook height.

Local shear texture formation in adiabatic shear bands by high rate compression of high manganese TRIP steels

Local shear textures in ASBs of high manganese TRIP steels under high rate straining are determined and the influences of initial microstructure is analyzed using EBSD technique. It is seen that even at the presence of majority of two types of martensite before deformation, ASB is preferred to evolve in austenite, rather than in martenite, due to reverse transformation. Ultrafine grains of thress phases due to dynamic recrystallization are formed and all show shear textures. The less ε-martensite in ASB is distributed as islands and its preferred orientation can be found to originate from the variants in matrix. The grain orientation rotation around ASB in multi-phase alloy reveals significant influence of α'- martensite on texture in ASB. The mechanism of local texture formation in ASB of high manganese TRIP steel is proposed in terms of the interaction of early TRIP and later reverse transformation.

Microstructure and mechanical properties of multi-pass friction stir processed aluminum alloy 6063

The effect of overlapping between consecutive passes of Friction Stir Processing (FSP) was examined on the microstructure, microtexture, and mechanical properties of Al 6063. FSP was carried out at three overlapping (OL) percentages, i.e. 25, 50, and 75, and at constant rotational and traverse speeds of the FSP tool. Microstructural analysis based on grain boundary misorientation distribution, grain size and microtexture were made by Electron Back Scattered Diffraction (EBSD), while mechanical properties were evaluated by microhardness and tensile tests. For the three OL percentages, similar grain refinement (in the range of 3–6μm) occurred in the processed zone. The microtexture measurements in the OL area show the formation of shear texture, having a stronger intensity of B/B¯ component by increasing the OL percentage. On the other hand, the tensile and microhardness tests indicate a reduction in the strength and microhardness of FSP samples with increasing the OL percentage due to the dissolution of the hardening precipitates. The overlapping effect was further evaluated on the thermal stability of microstructure, microtexture, and mechanical properties of FSP samples by applying solution heat-treatment and aging (SHTA). The results show that SHTA led to grain growth with an average grain size of 35μm. However, it caused limited weakening of the shear texture in the OL area with no sign of recrystallization. In addition, SHTA led to precipitate formation and thus restoring the strength and microhardness to the levels of the base metal.

The different effects of asymmetric rolling and surface friction on formation of shear texture in aluminium alloy AA5754

Conventional rolling and asymmetric rolling (ASR) processes were applied to aluminium alloy AA5754 with different roll metal frictional conditions. The rolling textures were determined by X-ray diffraction technique and the formation of shear texture was studied. It has been demonstrated that the ASR and friction have different effects on the generation of shear texture. The ASR forces the deformation texture to rotate about the transverse direction from the fcc plane strain compression texture, while a high friction generates a so called ideal fcc shear texture consisting of the {001}〈110〉 and {111}〈uvw〉 components. The effect of ASR penetrates throughout the sheet thickness, but that of friction exists only from the sheet surface to one-quarter thickness.

Improvement in the r-value of aluminum sheets by differential-friction rolling

Differential-speed rolling can improve the formability of aluminum alloys through the formation of shear texture. The authors propose an alternative asymmetric rolling method. The asymmetry is achieved by differentiating the friction on the upper interface from that on the lower interface. A commercial aluminum sheet in which one surface was coated with PTFE was rolled. The shear strain introduced was comparable to that introduced by differential-speed rolling. The annealed sheet showed a higher r-value than the symmetrically rolled sheet.

Shear Texture Formation during High-Strain Torsion of Titanium Aluminides

Ti-47Al-4(Cr, Nb, Mn, B) samples with different initial grain structures and fibre textures were deformed in torsion at 1000 °C under hydrostatic pressure of 400 MPa in a Paterson type rock deformation machine at a maximum constant strain rate of 2*10-4 s-1. The microstructure was investigated by transmission electron microscopy (TEM). Local texture measurements as a function of shear strain were done with high-energy synchrotron radiation. During shearing due to dynamic recrystallization the initially lamellar structure breaks down into a fine-grained globular structure with a g grain size in the order of 5 µm. The shear texture developed consists of <110> and {110} inclined to the shear direction and shear plane, respectively. The microstructure and texture development is discussed.

Formation of Shear Texture and Ultra-Fine Grains during Equal Angular Channel Rolling and Subsequent Annealing in AA 3003 Sheet

The evolution of texture and microstructure during the equal channel angular rolling (ECAR) and subsequent annealing in aluminum alloy 3003 sheets was investigated. The tools of ECAR were designed to provide a constant shear deformation of the order of 0.5 per passage while preserving the original sheet shape. Samples of the aluminum alloy 3003 sheets were repeatedly deformed by ECAR up to twelve passages. Shear textures developed after the first passage of ECAR. However, the intensity of shear texture components decreased with increasing number of ECAR passages. After a large number of ECAR passages, a random texture developed at the expense of shear texture components. Observations by TEM and EBSD revealed that the degree of misorientations within the deformed grains increased with increasing number of ECAR passages. After recrystallization annealing, samples deformed by ECAR displayed pronounced {111}//ND fiber orientations. The annealed sheets comprising of ultra-fine grains were successfully produced in the samples deformed by a large number of ECAR passages.

Formation of Shear Texture and Ultra-fine Grains in Warm Rolled AA 3004 Sheets

Formation of Shear Texture and Ultra-fine Grains in Warm Rolled AA 3004 Sheets

Modeling of rolling texture in aluminum

In comparison with the rolling texture modeling based on the Sachs, Taylor and modified Taylor assumptions a modified Sachs model was proposed, in which the equilibrium of both stresses and strains among the deformed grains is considered and therefore the shear strains are partially constrained by activation of other slip systems besides the primary one. The modeling predicts more details of the rolling texture that observed frequently in rolling aluminum sheets, and the model calculation could include the influence of initial texture. The parameters for homogeneous rolling are reported and the shear texture formation is also discussed.

Structural peculiarities of the 123 and 2212 phases and materials based on them

The refinement of structure parameters, chemical composition and T c of mono- and polycrystalline YBa 2Cu 3O 7− x , GdBa 2Cu 3O 7− x , DyBa 2Cu 3O 7− x and Bi 2Sr 2CaCu 2O 8+ x samples illustrate sharp correlations of the peculiarities of the crystal structures with the oxygen content and T c level. Crystal anisotropy of the yttrium- and bismuth-based high-temperature superconducting 123 and 2112 phases under cold and warm plastic strip deformation gives rise to the formation of a basal texture, the perfection and stability of which are determined by the conditions of deformation, and subsequent annealing and phase transformations. The T c level of polycrystalline materials depends slightly on the formation of basal texture and is determined by their substructure. The formation of shear texture in the yttrium-based high-temperature superconducting strips drastically decreases their T c.

The influence of the geometry of rolling on the formation of texture inhomogeneity

The problem of texture inhomogeneity is usually demonstrated in practice as formation of shear texture in cold rolled material. It has been discussed by the authors in the literature from the point of view of the influence of technological parameters on the deformation process as well as the analyses of the texture in particular layers of a sheet [1.2] and the penetration of shear texture into the rolled material [3]. It was found that the technological parameters of rolling such as: geometry of the rolling gap, coefficient of friction and the rate of rolling play an important role in the shear texture formation. Moreover, it was stated that the necessary condition but not a sufficient one for the shear texture to appear on the surface is the respectively high value of the geometrical parameter of rolling l/h where: 1 is the projected lenght of contact between the roll and the material and h is the mean thickness of the sample. Tselikov [4] predicted that depending on the value of the geometrical parameter l/h the distribution of the normal stress pc and unit friction forces T can be changed which is schematicaly shown in figure 1.