Analysis of deformation textures of asymmetrically rolled aluminum sheets

Asymmetric rolling, in which the circumferential velocities of working rolls are different, imposes shear deformation and in turn shear deformation textures to sheets through the thickness. A component of ND//〈111〉 in the shear deformation textures can improve the plastic strain ratios of aluminum sheets. In order to understand the evolution of ND//〈111〉, the strain histories and distributions in the sheets and the texture evolution during the asymmetric rolling have been measured and calculated. The shear deformation texture can vary with the ratio of shear to normal strain increments. As the ratio increases from zero to infinity, the texture moves from the plane strain compression texture (β fiber) to the ideal shear deformation texture consisting of {001}〈110〉, {111}〈110〉, and {111}〈112〉. The ratio increases with rolling reduction per pass in asymmetric rolling. However, it is practically difficult to develop a rolling reduction per pass high enough to obtain the ideal shear deformation texture. Imposing the positive and negative shear deformations on the sheet by reversal of the shearing direction can give rise to the ideal shear deformation texture.     

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}<110> 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}<110> 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.     

异步轧制对高纯铝箔冷轧织构的影响

通过异步轧制，对高纯铝箔微取向流变行为进行了研究，结果表明，异步轧制与同步轧制的冷轧织构有较大差异，高纯铝箔在异步轧制下慢辊和快辊两侧的织构类型明显不同，尤其是旋转立方织构{001}{110}在含量上的差异更大，快辊侧随形变量的增中冷却织构主要为：S织构和{102}{uvw}织构，而慢辊侧则主要为：旋转立方织构{001}{110}，慢辊侧的旋转立方织构在相同的速比、相同的形变量下一般要大于快辊侧的旋转立方织构。     

Experimental and simulation textures in an asymmetrically rolled zinc alloy sheet

The crystallographic textures developed in a zinc–copper–titanium (ZnCuTi) alloy sheet during asymmetric rolling have been studied. The strain history undergone by the sheet has been calculated by an elasto-plastic flow line model. The so obtained successive strain increments have been used as input data to a Taylor model, to simulate the corresponding texture evolution in the sheet. It is shown that the shear strain is the dominant factor that governs the texture evolution during asymmetric rolling.     

润滑剂对高纯铝形变织构的影响

采用ODF法（晶体取向分布函数法）研究和分析了润滑剂对高纯铝冷轧形变织构的影响,揭示了两种润滑条件下形变织构的演变规律。结果表明:大冷轧变形程度下,采用机油润滑,形变织构为典型的面心立方金属的轧制织构,即由强的B-、Cu-及S-织构组分构成,而且取向分布的密度峰值处在S-取向位置;煤油润滑时轧制织构相对较弱,但Cu织构最强,同时产生了明显的剪切织构{001}<110>（Rot.Cube-织构）。采用机油润滑时,轧制变形比较均匀。低变形轧制时晶粒取向聚集于α线,随变形量的增加,向β线取向聚集,大变形量下最终形变织构为铜型轧制织构;而煤油粘度小,轧制过程中接触表面摩擦因数较大,不均匀变形严重,低轧制程度时发现有表面剪切Rot.Cube-织构,随着塑性变形的增大,Rot.Cube-织构逐渐向Cu-取向转化;变形至95％后,随着变形程度的增加,S-织构减弱。     

润滑对3104铝合金板变形织构的影响

在无润滑(WOL)和润滑(WL)2种轧制条件下,分别对2.3 mm厚的热轧3104铝合金板进行不同压下量的冷轧.应用取向分布函数(ODF)定量计算和分析在不同轧制压下量下润滑对3104铝合金板材沿板厚方向织构演变的影响.结果表明:随着轧制压下量的增加,样品各层的织构组分强度均逐渐增加;无润滑轧制时样品表面层主要织构组分取向密度普遍高于相同压下量下润滑轧制时的取向密度.导致表面层织构组分增强的原因是摩擦引起应变状态改变的结果.     

特殊成形工艺下AZ31镁合金的织构及变形机制

通过组织观察以及宏观和微观织构测定、分析了异步轧制及等径角轧制的AZ31镁合金形变机制,确定了在这两种工艺下{0001}基面织构的改善效果.结果表明:异步轧制产牛的平行于轧面的剪切力促进了与普通轧制状态下相反的基面滑移,使基面织构连续地弱化为倾转的基面织构;而等径角轧制通过产生与轧向成122.5°的剪切力,使基面取向的晶粒产生拉伸孪晶,形成与基面织构共存的柱面织构.因此这两种特殊工艺都可能改善镁合金的塑性.还分析了形变量和退火对织构的影响.     

Textures variation of 3104 aluminum alloy sheets under different rolling conditions

1　INTRODUCTIONLargequantityoftheAl Mn Mgalloy 310 4isusedinthemanufactureofaluminumbeverage .Muchattentionwaspaidtothecontroloftextureandearinginthedeepdrawingstagesofmanufacture .Thetex tureinthecanstockwasextensivelyinvestigated .Oneearingofaluminumalloyisverycloserelatedtothetexture ,agoodassociationofthetexturescompo nentsearingdropsobviously ,inthissituationthe 4 foldearingat 0°/90°andearingat± 4 5°occursto gether[15] .Theappearanceof 4 foldearingat 0°/90°isduetothecubetext…     

PRIMARY RECRYSTALLIZATION TEXTURES OF 70-30 BRASS ROLLED BY CROSS SHEAR ROLLING IN SINGLE DIRECTION

ＰＲＩＭＡＲＹＲＥＣＲＹＳＴＡＬＬＩＺＡＴＩＯＮＴＥＸＴＵＲＥＳＯＦ７０－３０ＢＲＡＳＳＲＯＬＬＥＤＢＹＣＲＯＳＳＳＨＥＡＲＲＯＬＬＩＮＧＩＮＳＩＮＧＬＥＤＩＲＥＣＴＩＯＮ￥ＺｈａｏＸｉａｎｇ；ＬｉｕＹａｎｓｈｅｎｇ；ＸｕＪｉａｚｈｅｎ；ＬｉａｎｇＺ...     

Influence of initial textures on dynamic recrystallization and textures in AZ31 magnesium alloys

1　INTRODUCTIONMagnesiumisthelightestmetallicstructurema terialwithhighspecificstrengthandthereforeiswidelyusedinautomotive ,electronicsandaerospaceindustries[1,2 ] .However ,magnesiumoftenshowsinsufficientplasticityatroomtemperatureduetoitsHCPstructurewithlessindependentsystemsofbasalslip .Toenhanceformabilityofmagnesium ,ahigherdeformingtemperatureisusuallyusedwithtwopur poses .Thefirstistoactivatenewslipsystemsbesidesbasalslip ,sothatmorethanfiveindependentslipsystemscanbeprovided ,be…     

The effect of roll gap geometry on microstructure in cold-rolled aluminum

Microstructure and texture are analyzed through the thickness of two aluminum plates cold-rolled 40% with different roll gap geometries. It is found that both texture and microstructure are strongly affected by the rolling geometry. After rolling with intermediate-size draughts a rolling-type texture is developed throughout the plate thickness. In this case, grains are subdivided by extended planar dislocation boundaries preferentially aligned at an angle of 40 ± 15° to the rolling direction. In the plate rolled with small draughts, shear texture components appear in the intermediate layers. In these layers, extended planar dislocation boundaries are frequently found to be inclined closely to the rolling direction. The subsurface and central layers of this plate exhibit microstructures similar to those in the plate rolled with intermediate draughts. It is suggested that the development of different textures and microstructures at different depths is related to the activation of different slip systems due to through-thickness strain gradients.     

Texture Distribution and Plane Strain Mechanical Behavior of AA 7xxx Plates of Different Thicknesses

Texture distribution of a rolled aluminum alloy type AA 7449 plate having two thicknesses is presented here. The mechanical behavior of these aluminum alloy plates under plane strain compression (PSC) was studied under different shear stress textures. Crystallographic texture of specimens was characterized by x-ray diffraction and the corresponding volume fractions of each texture component were determined. The obtained results show that shear stress texture components are concentrated at layers immediately below the surface, as it had been previously proposed. Additionally, specimens were subjected to hot PSC to mimic industrial hot rolling process under controlled conditions. The measured rheological parameters, strain rate sensitivity coefficient m, and activation energy Q, show that the mechanical behavior under PSC is more sensitive to test conditions than to the shear stress texture.     

Analysis of microstructure and texture evolution in pure magnesium during symmetric and asymmetric rolling

Asymmetric rolling of commercially pure magnesium was carried out at three different temperatures: room temperature, 200 °C and 350 °C. Systematic analysis of microstructures, grain size distributions, texture and misorientation distributions were performed using electron backscattered diffraction in a field emission gun scanning electron microscope. The results were compared with conventional (symmetric) rolling carried out under the same conditions of temperature and strain rate. Simulations of deformation texture evolution were performed using the viscoplastic self-consistent polycrystal plasticity model. The main trends of texture evolution are faithfully reproduced by the simulations for the tests at room temperature. The deviations that appear for the textures obtained at high temperature can be explained by the occurrence of dynamic recrystallization. Finally, the mechanisms of texture evolution in magnesium during asymmetric and symmetric rolling are explained with the help of ideal orientations, grain velocity fields and divergence maps displayed in orientation space.     

A Review of Texture Evolution Mechanisms During Deformation by Rolling in Aluminum Alloys

The current understanding of texture evolution during deformation by rolling in aluminum alloys was summarized. This included understanding the evolution mechanisms and several key factors of initial texture, microstructure, alloy composition, deformation temperature, stress–strain condition, and rolling geometry. Related models on predicting texture evolution during rolling were also discussed. Finally, for this research field, the recommendations for controlling the formation of rolling textures were proposed.     

Study on the cold rolling deformation behavior of polycrystalline tungsten

Tungsten is paid special attention due to its superior properties, especially in nuclear field. Meanwhile it is suitable for texture simulation investigation of BCC metals and alloys as it's near elastically isotropic. This study investigates the cold rolling deformation texture of polycrystalline tungsten using RS model, in which the stress and strain consistence is realized simultaneously. The texture evolution and effects of deformation parameters, including external as well as internal reaction stress, strain and activation of different slip, on texture during rolling are discussed by comparing the simulated results and reported experimental results in literatures. The results show that, the cold rolling deformation texture could be simulated statistically based on RS model. The accumulation of each reaction stress is different. The up-limit of reaction stress σ'₁₂ is found to be medium, meaning that σ'₁₂ exerts important effect on texture evolution. Much lower accumulation level of σ'₁₃ as well σ'₂₃ is displayed, each of which within certain range contributes to the increase of different γ-fiber texture components. The effect of σ'₂₂ can't be ignored during rolling, especially in the case of obtaining {111}<110> texture. Regarding the deformation textures of tungsten rolled to true strains of −1.7 and −2.91, {001}<110> texture is strengthened with the increasing strain and becomes dominant, implying the easier activation of {112}<111> slip systems; γ-fiber texture is weakened at higher strain, and the formation of {111}<112> texture shows significant effect of surface shear stress σ₁₃, which is due to the nonnegligible surface friction when rolling at high temperature.     

Evolution of through-thickness texture gradients in various steel sheets

In order to investigate the evolution of through-thickness texture gradients in various ferritic steel sheets, samples of a deep drawing steel, a ferritic stainless steel and a low carbon steel were deformed by cold rolling with and without application of a lubricant during the deformation process. The hot band texture of all samples examined showed notable through-thickness texture gradients. The evolution of the cold rolling texture in the ferritic stainless steel and the low carbon steel in a solution-treated state was nearly independent of the lubrication during rolling. However, in the deep drawing steel and the as-received low carbon steel, the lubrication played an important role in the formation of the through-thickness texture gradients. Whereas the samples rolled with lubrication showed uniform textures throughout the sheet thickness, in the samples rolled without lubrication pronounced shear textures were observed on the sheet surface. The evolution of these through-thickness texture gradients is discussed in terms of inhomogeneous strain states computed by an FEM model. This article is based on a presentation made in the symposium “ ’99 International Symposium on Textures of Materials”, held at Sunchun National University, Sunchun, April 21–22, 1999 under the auspices of The Korean Institute of Metals and Materials and The Research and Development Center for Automobile’s Parts and Materials.     

COLD ROLLING AND RECRYSTALLIZATION TEXTURE OF CROSS SHEAR ROLLED COMMERCIAL COPPER

The texture change along the normal direction to rolling plane of cross shear rolled commer-cial copper has been studied by means of two step method for ODF caleulation and computersimulation.The texture of cross shear rolling of copper is similar in primary components tothat of conventional cold rolling,but the scattering degree and direction of the texture are dif-ferent,due to the residual shear strain change in different position along the normal to rollingplane.It seems that no more effect of the shear strain upon the recrystallization texture.     

Orientation dependence of shear banding in face-centered-cubic single crystals

We present crystal plasticity finite element simulations of plane strain compression of α-Brass single crystals with different initial orientations. The aim is to study the fundamentals of mesoscale structure and texture development in face-centered-cubic (fcc) metals with low stacking fault energy (SFE). Shear banding depends on the initial orientation of the crystals. In Copper and Brass-R-oriented crystals which show the largest tendency to form shear bands, an inhomogeneous texture distribution induced by shear banding is observed. To also understand the influence of the micromechanical boundary conditions on shear band formation, simulations on Copper-oriented single crystals with varying sample geometry and loading conditions are performed. We find that shear banding can be understood in terms of a mesoscopic softening mechanism. The predicted local textures and the shear banding patterns agree well with experimental observations in low SFE fcc crystals.     

Role of shear band in texture control of Al-Mg alloys

Shear bands formed in Al-Mg alloys during cold rolling are nucleated on grain boundaries. Their mechanism of formation is different from that already proposed in the case of single crystals of the same alloy. Since recrystallized grains of non-cube orientations are nucleated on these shear bands during annealing, the development of cube recrystallization texture can be strongly suppressed by enhancing shear banding during cold rolling. Control of shear band thus provides a new fundamental technological tool to improve drawability of Al alloy sheets. In a microscopic scale, deformation in grain boundary regions also plays here a very important role, as in the case of the formation of {111}uvw recrystallization textures in low carbon steel sheets.     

Non-crystallographic shear banding in crystal plasticity FEM simulations: Example of texture evolution in α-brass

We present crystal plasticity finite element simulations of the texture evolution in α-brass polycrystals under plane strain compression. The novelty is a non-crystallographic shear band mechanism [Anand L, Su C. J Mech Phys Solids 2005;53:1362] that is incorporated into the constitutive model in addition to dislocation and twinning. Non-crystallographic deformation associated with shear banding leads to weaker copper and S texture components and to a stronger brass texture compared to simulations enabling slip and twinning only. The lattice rotation rates are reduced when shear banding occurs. This effect leads to a weaker copper component. Also, the initiation of shear banding promotes brass-type components. In summary the occurrence of non-crystallographic deformation through shear bands shifts face-centered-cubic deformation textures from the copper type to the brass type.