Papers by Keyword: Texture Evolution

Abstract: Fe-6.5wt%Si steel is an excellent soft magnetic material due to the near-zero magnetostriction and low core losses. In this study, a 0.3 mm-thick grain-oriented 6.5wt%Si steel sheet was produced by a novel strip casting and two-stage rolling. The microstructure and texture evolution were investigated with a special emphasis on the nucleation and growth of Goss grains. The thin normalized strip was composed of large columnar grains and small equiaxed grains. During intermediate annealing, Goss grains nucleated in the shear bands of the deformed <111>//ND grains, and the deformed {111}<112> grains provided most of the nucleation sites. After primary annealing, the Goss grains distributed across the entire thickness, which was different from the conventional rolling route. The fraction of high-angle boundaries (20°-45°) surrounding the Goss grains was apparently higher than those of the matrix grains, which promoted the abnormal growth of the Goss grains during secondary recrystallization.

Abstract: Texture evolution in two magnesium alloys, Mg-4%Zn-1%Nd and Mg-1%Zn-1%Nd (weight percentage), was studied after rolling and the subsequent isothermal annealing. The finish rolling was completed in a single pass with a thickness reduction rate of ~30% at 100 °C and a rolling speed of 1000 m/min. After cooling to room temperature, the rolled samples were annealed at 350 °C for different annealing times. Upon annealing, the maximum intensity of the basal pole texture decreases as recrystallization progresses. In the Mg-1Zn-1Nd alloy (with a high Nd/Zn ratio), texture weakening is maintained even after complete recrystallization and grain coarsening, while in the Mg-4Zn-1Nd alloy, texture strengthening occurs after grain coarsening, and a single peak replaces the double split basal peaks. In the Mg-1Zn-1Nd alloy, grain coarsening is accompanied by a bimodal grain size distribution, whereas in the Mg-4Zn-1Nd alloy, the grain coarsening leads to a uniform grain size distribution. TEM investigations show the formation of the Zn and Nd rich clusters at early stage of annealing in both alloys. During recrystallization, these clusters were dissolved in the Mg-4Zn-1Nd alloy, but they are more stable in the Mg-1Zn-1Nd alloy. In our opinion, the formation of these stable clusters is one of the main factors for texture weakening of the Mg-Zn-RE alloys.

Abstract: In this study, texture evolution during high pressure torsion (HPT) of aluminum single crystal is predicted by the crystal plasticity finite element method (CPFEM) model integrating the crystal plasticity constitutive theory with Bassani & Wu hardening model. It has been found by the simulation that, during the HPT process, the lattice rotates mainly around the radial direction of the sample. With increasing HPT deformation, the initial cube orientation rotates progressively to the rotated cube orientation, and then to the C component of ideal torsion texture which could be remained over a wide strain range. Further HPT deformation leads to the orientation towards to the ideal texture component.

Abstract: The flow curve behavior and microstructure evolution of commercially pure titanium (CP-Ti) through uniaxial hot compression was investigated at 850 °C and a strain rate of 0.1/s. Electron back scattered diffraction (EBSD) was employed to characterize the microstructure and crystallographic texture development for different thermomechanical conditions. The stress-strain curves of CP-Ti alloy under hot compression displayed a typical flow behavior of metals undergoing dynamic recrystallization (DRX), which resulted in grain refinement. The critical strain for the onset of DRX was 0.13 using the double differentiation analysis technique. It was also revealed that the texture was markably altered during hot deformation.

Abstract: Thick plate and sheet materials are often characterised by an inhomogeneous distribution of properties such as yield strength and anisotropy throughout their thickness. Forming of these materials involves further heterogeneous evolution of these properties. A recently developed computational framework [1, now allows these heterogeneities to be modelled via a hierarchical multi-scale material modelling scheme: the evolution of texture and plastic anisotropy can be tracked and individually updated at every integration point in a finite element model, in a computationally efficient manner. In this paper we present the application of this multi-scale model to a benchmark forming simulation, the three point bending test of thick plate steels. A number of hot rolled high strength low alloy steels were considered, two of which are presented here. The results of the simulations are validated against experimental results. Comparison is made between computed and experimental deformed shapes and strain fields, using data acquired by digital image correlation. Predictions of heterogeneously evolved textures are compared with experimental macro-textures, acquired by XRD, at key locations in the final deformed samples. Such models for plate steel forming simulations that are able to provide accurate predictions of deformation textures and derived quantities in the entire volume of the material can be crucial to study further processing steps and properties of the final product.

Abstract: A new approach to dynamic recrystallization (DRX) is introduced. It is based on the assumption that the critical conditions for DRX and the arrest of DRX grain boundaries are related to the development of mobile subboundaries. The theoretical predictions are compared to experimental results during incipient and steady-state DRX. The grain size sensitivity of the DRX grains establishes the desired link between deformation and DRX microstructure.

Abstract: A typical car stamping is analyzed in terms of FEM and its press signature is evaluated in detail. Microstructural, crystallographic texture and surface roughness evolution are studied in conjuntion with press performance. Careful press signature calibration is discussed in order to point out relevant aspects. Deep drawing steels are analyzed in terms of their evolution in microstructure and texture and path-related to the FLD (Forming Limit Diagram). 3D-Surface roughness is tentatively evaluated and related to the steel stampability.

Abstract: The 'stack' model of a rate-independent rigid-plastic polycrystalline material is developed. In the 'stack' model, stacks of N neighboring sub-grain domains collectively accommodate the imposed macroscopic deformation while enforcing the velocity and traction continuity condition with its neighbors. The developed 'stack' model is applied to simulate the two-dimensional polycrystalline aggregate under macroscopically imposed plane-strain tension. The effect of inter- and intra-grain interactions on qualitative and quantitative variations in the predicted macroscopic stress-strain response and texture evolution are presented. The diminishing trend of constraint on individual sub-grain domains and texturing rate with stack size N, and saturation for large N also given.

Abstract: In the present study, in situ phase transformation experiments have been carried out using neutron diffraction to monitor the texture evolution during the α→ß→α phase transformation in Ti-6Al-4V with and without 0.4% yttrium additions. The aim of adding yttrium was to control ß grain growth above the transus ß by grain boundary pinning. In the present case, strengthening of the ß texture, occurring during ß grain coarsening resulted in strengthening of particular ß texture components, which increases the likelihood of α texture modification by selective growth of α variants on the common (110) ß grain boundaries into unoccupied large β grains.

Abstract: 0.2mm-thick high silicon steel thin sheet under 94% cold rolling reductions has been successfully produced by conventional rolling method. Texture evolution during hot rolling, cold rolling and final annealing as well as magnetic properties has been investigated with emphasis on the effect of finishing temperature. It is found that a favorable strong {001}<210> recrystallization texture and evidently improved magnetic properties can be obtained at the finishing temperature of 900°C, which is in contrast with relatively strong detrimental {111}<112> and weak {001}<210> recrystallization texture at the finishing temperature of 700°C. Effects of finishing temperature can be explained in terms of the cold rolling texture due to different texture morphology in hot bands.