Development Of Rolling Textures Research Articles

Micro-mechanisms of deformation texture evolution in nanocrystalline nickel-cobalt alloys

Deformation mechanisms in nanocrystalline Ni-x wt% Co alloys (x = 0, 20, 40, 60), having stacking fault energy values from high to low, have been investigated with regard to the evolution of microstructure and texture during room temperature rolling. In all the materials, no new texture peak appears until 20% thickness reduction and the texture is similar to initial fiber texture, which indicates that grain boundary-mediated deformation mechanisms are more active. The development of characteristic copper-type and brass-type rolling textures is visible beyond 40% reduction. High SFE materials, namely pure Ni and Ni-20Co alloy, develop a copper-type texture at large reduction, whereas in low SFE Ni-40Co and Ni-60Co alloys, the texture is close to brass-type. The evolution of copper-type texture is attributed to the activity of ½{111}<110> type dislocations and cross slip in nanocrystalline grains, which is aided by deformation-driven grain growth. Crystal plasticity simulations suggest that the evolution of brass-type texture evolution in low SFE nanocrystalline alloys is due to 1/6{111}<112> type partial dislocation slip. The activity of partial slip is promoted by the suppression of grain growth and cross slip in high cobalt containing alloys. The evolution of deformation texture and microstructures in nanocrystalline nickel-cobalt alloys is governed by the combined effects of grain size and SFE.

Evolution of hot rolling texture in pure tungsten and lanthanum oxide doped tungsten with various reductions

Textures of hot rolled pure tungsten (PW) and W-1.0wt%La2O3 (W-1%La2O3) with various strains were characterized to figure out the effect of rolling reduction and second phase on evolution of hot rolling texture. Initial sintering texture of 〈111〉//ND and {110}〈111〉, {112}〈111〉 slip systems as well as dynamic recovery, dynamic recrystallization facilitated the formation of the θ-fiber and γ-fiber textures for PW and W-1%La2O3 during the hot rolling process. Furthermore, dynamic recovery occurred in 72% rolled PW and 43% rolled W-1%La2O3 led to a significant rise of {001}〈110〉 texture. Besides, dynamic recrystallization occurred in 80% rolled PW and 72% rolled W-1%La2O3 resulted in an enhancement of {001}〈100〉accompanied with a drop of {111}〈112〉texture. The occurrence of dynamic recovery and dynamic recrystallization in W-1%La2O3 was sooner than in PW, which may be caused by more dislocations in total and additional geometrically necessary dislocations as well as local deformation zone induced by adding of La2O3 particles.

Ti/Al Multi-Layered Sheets: Differential Speed Rolling (Part B)

Differential speed rolling has been applied to multi-layered Ti/Al composite sheets, obtained from accumulative roll bonding with intermediate heat treatments being applied. In comparison to conventional rolling, differential speed rolling is more efficient in strengthening the composite due to the more pronounced grain refinement. Severe plastic deformation by means of rolling becomes feasible if the evolution of common rolling textures in the Ti layers is retarded. In this condition, a maximum strength level of the composites is achieved, i.e., an ultimate tensile strength of 464 MPa, while the strain to failure amounts to 6.8%. The deformation has been observed for multi-layered composites. In combination with the analysis of the microstructure, this has been correlated to the mechanical properties.

Through-thickness texture in clock-rolled tantalum plate

135° clock rolling, which denotes that the rolling direction clockwise rotates 135° after per pass, was utilized to develop a desired cold-rolled texture distribution through the thickness of Ta plate. Meanwhile, the influence of starting texture and microstructure was also investigated in detail. Texture from surface to center of the initial and rolled Ta plates was characterized by X-ray diffraction (XRD). In order to explore the correlation between initial microstructure and the evolution of rolling texture, through-thickness microstructure of the initial Ta plate was observed by optical microscope (OM). Results showed that 135° clock rolling was effective to mitigate the through-thickness texture gradients often existing in cold-rolled tantalum plate. It was found, furthermore, that texture and microstructure prior to rolling play a particular role in the formation of rolling texture.

Texture Evolution of Commercially Pure Copper during Ultra-Thin Strip Rolling

Experimental investigation on rolling texture evolution in commercially pure copper thinned from 5.8mm to 20μm by symmetrical rolling and asymmetrical rolling without annealing were carried out via orientation distribution functions and orientation line analysis. The results show that the rolling texture for the sample with initial rotate cube texture {100}&lt;011&gt;mainly consist of C and B, most crystallites aggregate along the α and β orientations lines. The texture density growth rate increased significantly in rolling process. That may relate to size effect of ultra-thin strip. The rate of dislocation reduction was more than dislocation multiplication due to disappear at grain size, when the thickness of ultra-thin strip decreased to an extremely value.

Deformation Texture and Microstructure Evolution in Nickel and Nickel-Cobalt Alloys

Rolling texture evolution of pure nickel, and nickel – cobalt alloys containing 20wt.%, 40wt.%, 60wt.% cobalt content has been studied to very large true strain (ε ~ 4). The texture evolution in pure nickel and Ni-20Co was very similar, and resulted in typical Cu-type rolling texture. Microstructural analyses showed that the deformation was mostly slip dominated up to 95% beyond which it shear bands. Deformation twinning was a major deformation mechanism up to 50% reduction, and at higher strains, microstructure showed extensive shear banding. The evolution of final Goss texture in low SFE Ni-Co alloys could be explained based on the twin fraction and shear band volumes which showed grains preferably oriented towards Goss.

Texture transition in cold-rolled nickel–40 wt.% cobalt alloy

The micromechanical aspects of rolling texture development in Ni–40wt.% Co alloy during very large reductions (up to εt=3.9) have been studied. The alloy showed a typical Cu-type texture up to a true strain of εt=3; however, the texture undergoes an abrupt transition to Bs-type on further rolling to εt≈4. (The Bs-type texture, here, comprises almost equal fractions of Goss and Bs components.) Microstructural observations, at early stages, show that deformation is accommodated entirely by slip, and very little presence of deformation twinning is observed to explain the texture transition. However, at much higher reduction levels, micrographs show a high fraction of Cu-type shear bands. These bands are predominantly found in Cu-oriented grains and the crystallites inside the shear bands are preferentially oriented towards Goss, which could explain the final texture evolution.

INFLUENCE OF COLUMNAR GRAINS ON THE COLD ROLLING TEXTURE EVOLUTION IN Fe--3%Si ELECTRICAL STEEL

Columnar grains exist in nearly all cast slabs of Fe-3%Si electrical steels,their morphological and crystallographic anisotropies strongly influence the microstructure and texture evolution during following hot rolling,cold rolling and final annealing.This work investigates the rolling texture and microstructure of the specimens with columnar grains initially arranged along different directions by means of XRD and EBSD techniques,and the effects of columnar grain boundaries are analyzed.The results show that at intermediate rolling reduction,all three types of specimens show to different extents the inheritance of {001} texture,or in other words,they prevent effectively the formation of {111} texture.The {001} texture is strongly retained in ND specimen (with initial columnar grains' longitudinal axis being along normal direction) and TD specimen(with initial columnar grains' longitudinal axis being along transverse direction),whereas {111}112 texture is the strongest in RD specimen(with initial columnar grains' longitudinal axis being along rolling direction).In addition,rotated cube and {111}110 textures develop in TD specimen.All three types of specimens demonstrate an orientation rotation path from cube {001}100 over 20°rotated cube {001}130 to {113}251,which is in contrast to the conventional rotation path fromαfiber toγfiber in equiaxed polycrystalline electrical steels.In spite of the significant difference in grain boundary arrangement in the three types of specimens,their influence on texture formation is limited because of the large grain sizes and the influence is mainly related with initial orientations. To understand rolling texture evolution of columnar grain specimens is of great significance in the development of new type electrical steels with strong {001} texture.

The Effect of Strain Field on Texture and Microstructure Evolution in Homogeneously Cold Rolled 93/7 Brass

In this study, SEM and Köhlhoff etching were employed to follow the rolling texture and microstructure development in 93/7 brass that had been homogeneously cold rolled to different plastic strains. Correlated with FEM to rolling process, the effect of strain field on rolling texture and microstructure development in rolled 93/7 brass is conducted and reasonable conclusion is obtained.

The Effect of Mill Temperature on the Texture and Microstructutre Evolution in Warm Rolled α-Brass

At the entrance temperature of 300°C, the effect of mill temperature on the texture and microstructure evolution was worked to 85/15 α-brass by two rollings with mill temperatures calibrated as 28°C for one rolling and 55°C for another, in which TEM was employed to reveal the microstructures, and ODF to represent the related textures. From the experiment evidence, a detailed discussion was made and led to a conclusion: in current rolling, with recovery, mill temperature influences the rolling texture and microstructure development through chilling and the working temperature induced deformation mechanisms change, the former one affecting B intensities, by contrast, the latter one leading to a texture transition.

Coupled effects of the lattice rotation definition, twinning and interaction strength on the FCC rolling texture evolution using the viscoplastic ϕ-model

Prediction of the rolling texture evolution in FCC metals is controlled by interaction laws, deformation mechanisms and definition of the lattice spin. The coupled effect of these three factors on the FCC rolling texture evolution is hereby analyzed using the viscoplastic ϕ-model. Without the Eshelby theory, this model yields an interaction law spanning predicted results from the upper to lower bound ones by varying a scalar weight parameter ϕ (0<ϕ<1). In this work, two definitions of the lattice spin, the mathematical analysis (MA) and the plane–strain analysis (PSA), are considered in the ϕ-model. The influence of the MA and PSA definitions on the FCC rolling texture evolution is deeply analyzed in conjunction with twinning and grain interaction strength, from a stiff to a more compliant interaction.

Prediction of Texture Evolution in Rolled Sheet Metals by Using Homogenization Schemes

This work deals with comparing the prediction of the development of rolling textures by using a homogenization method that is based on a homogeneous reference material. The proposed homogenization scheme, assuming constant stress polarisations in each phase, has in a natural way the potential to model the transition between Taylor- and Sachs-type textures. Therefore, the stiffness ef the hemogeneous reference material has to be varied between infinitely stiff and infinitely compliant. In the present study, texture evolution during rolling is simulated, showing that the application of different comparison materials in the homogenization scheme leads to the development of different main texture characteristics (Cube, Cu, Bs, Goss) in the orientation distribution function. For efficiently carrying out the rolling simulations using the proposed method, the measured texture information of the bulk aluminum sample is representatively reduced by using a partitioning technique of the orientation space.

Evolution of Hot Rolling and Phase Transformation Textures in an α″ (Orthorhombic) Phase in Ti-Nb Alloys

This work describes the development of texture during hot rolling of two alloys namely, Ti-12Nb and Ti-16Nb. The alloys have been unidirectionally hot rolled to 80 % reductions at 800°C and air cooled. Both the alloys show the presence of a² (orthorhombic) and small volume fraction of b (bcc) phases in hot rolled condition. The alloy Ti-12Nb exhibit moderate intensity texture while the alloy Ti-16Nb displays quite strong texture. The high overall intensity of texture in alloy Ti-16Nb in 80 % HR specimen can be attributed to the presence of large volume fraction of b phase in comparison to that of the alloy Ti-12Nb. This has been extended to study the textural changes after b solution treatment. This heat treatment consists of two types of phase transformations that are a² ® b ® a² and a² ® b ® a after water quenching and furnace cooling from β phase field.

PROGRESS AND APPLICATION OF PLASTIC FINITE ELEMENT METHOD IN METALS ROLLING PROCESS

The recent progress of plastic finite element method (FEM) and its application in rolling are introduced, including: (1) progress in rigid plastic FEM theory and application. It deals with the variational principle for rigid-plastic compressible materials, the uniqueness of extreme point of total power rate functional for hot rolling problem, and the examples of solving various rolling processes; (2) elastic-plastic FEM was used to analyze the normal longitude rolling and the special rolling processes, such as wedge rolling, cross wedge rolling and skew rolling; (3) fast-FEM for modeling to control a rolling mill. Now it becomes true that a FEM calculation for one pass flat rolling could be accomplished within 50—100 ms, which means it is possible to meet the requirement of on-line use for the process control to the rolling mill instead the traditional mathematics models; (4) multi- scale FEM simulation for rolling using cellular automata (CA) and FEM. Here the CA was used to simulate the recrystallization and transformation, and the temperature field, stress field and strain field were provided by FEM; (5) using crystal plasticity FEM to simulate the texture evolution during rolling. The crystal plasticity theory was put into the framework of the finite element method, to simulate the plastic deformation process at the crystal scale. An example is given for modeling of rolling Al polycrystal and texture evolution during the deformation; (6) FEM simulation of the crack and inclusion behaviors during rolling. The research works on evolution of cracks on the corner, edge, surface and inside of a workpiece, also for the inclusion by FEM are introduced. Finally, an outlook has been made for the plastic FEM.

Fast, Physically‐Based Algorithms for Online Calculations of Texture and Anisotropy during Fabrication of Steel Sheets

AbstractBecause of the complex microstructures of crystalline materials exposed to commercial manufacturing processes it is up to now not possible to obtain fast and on‐line simulations of crystallographic texture and anisotropy in the course of multiple deformation‐ and heat treatment procedures. In the present paper a hybrid approach for the on‐line texture and anisotropy prediction will be developed for the fabrication of low alloyed ferritic steel sheets during cold rolling and subsequent annealing procedures. Our approach is based on two consecutive models: The first one is an artificial neuronal network (ANN) for the description of the rolling texture evolution. The second one is an analytical, Avrami‐based texture component approach for the recrystallization. First results on low carbon steels will be presented.

Hot rolling textures of Al–Cu–Li and Al–Zn–Mg–Cu aeronautical alloys: Experiments and simulations to high strains

The development of hot rolling textures, and particularly the Brass {1 1 0} <1 1 2> component, of two typical aeronautical alloys: Al–Cu–Li AA2050 and Al–Zn–Mg–Cu AA7050, has been investigated by EBSD and X-ray diffraction measurements after plane strain compression tests and industrial hot rolling. Systematic hot channel-die compression tests were performed to strains of 2.7 at 420–450 °C, on both as-homogenized alloys. Under the same processing conditions, the two alloys develop the same rolling textures showing that the presence of Li is not intrinsically responsible for the development of strong Brass components. However, it is shown, by further channel-die compression tests between 350 and 500 °C and up to strains of 3.9, that the deformation temperature can have a major influence: with increasing temperature {1 1 0} <1 1 2> orientations are strongly favoured at the expense of the Copper {1 1 2} <1 1 1> component. Numerical simulations demonstrate that previous and current experimental observations of the influence of temperature on texture development can be explained by increasing slip on non-octahedral slip systems.

Evolution of Rolling Textures of Cold Rolled Copper Foils

The texture evolution of cold rolled tough pitch copper foils could be changed by altering the initial texture and microstructure before cold rolling. The development of β-fiber texture was substantially suppressed even after 92% reduction for the case of abnormally coarse initial grain structure and extremely strong initial cube texture. Instead, the intensity of cube and RD (rolling direction)-rotated cube texture components was increased continuously by increasing the intensity of the initial cube texture.

Modeling texture development during cold rolling of IF steel by crystal plasticity finite element method

With the consideration of slip deformation mechanism and various slip systems of body centered cubic (BCC) metals, Taylor-type and finite element polycrystal models were embedded into the commercial finite element code ABAQUS to realize crystal plasticity finite element modeling, based on the rate dependent crystal constitutive equations. Initial orientations measured by electron backscatter diffraction (EBSD) were directly input into the crystal plasticity finite element model to simulate the development of rolling texture of interstitial-free steel (IF steel) at various reductions. The modeled results show a good agreement with the experimental results. With increasing reduction, the predicted and experimental rolling textures tend to sharper, and the results simulated by the Taylor-type model are stronger than those simulated by finite element model. Conclusions are obtained that rolling textures calculated with 48 {110}〈111〉+{112}〈111〉+{123}〈111〉 slip systems are more approximate to EBSD results.

Development of Extrusion and Rolling Textures during ECAP of Mg-Alloys

Crystallographic texture includes much information on a material’s behaviour that depends on the processed material itself, the particular thermomechanical processing it has undergone, and the quality of the process. ECAP processed pure Mg and Mg alloys were characterised by their texture and are discussed in terms of texture symmetry. For all types of deformation, including ECAP, the basal plain orientation has to follow certain general rules. Particularly for larger number of passes the ECAP texture can be explained in terms of standard rolling or extrusion textures.

Texture evolution in grain‐oriented electrical steel during hot band annealing and cold rolling

The optimization of magnetic and physical properties of electrical steel is imperative for many engineering applications. The key factors to improve magnetic properties are the steel composition as well as control of the crystallographic orientation and microstructure of the steel during processing. However, this requires careful control of processing at all stages of production. Under certain conditions of deformation and annealing, electrical steel can be produced to have favourable texture components. For grain-oriented (GO) electrical steels that are used in most transformer cores, a pronounced {110} <001> Goss texture plays a vital role to achieve low power losses and high permeability. Essentially, Goss texture develops during secondary re-crystallization in GO electrical steels; however, the mechanism of the abnormal Goss grain growth is still disputed in the literature. In the current study, the influence of the annealing conditions on the development of annealing, cold rolling and re-crystallization textures of hot-rolled GO electrical steel were investigated in detail following each processing step. Furthermore, the orientation data from electron backscatter diffraction were used to evaluate the orientation-dependent stored energy of deformed grains after hot rolling. In the light of new findings in the present study, annealing and deformation texture development mechanisms were critically reviewed.