Papers by Keyword: Oriented Nucleation

Abstract: A new rolling process, which combined asymmetric rolling with symmetric rolling, was adopted in age-hardenable 6xxx series Al-Mg-Si alloy promising as automotive body panels in order to develop favorable textures for the deep drawability after solution treatment. Symmetric cold rolling at high reduction and subsequent asymmetric warm rolling at low reduction for AA6022 sheets led to the formation of “TD-rotated β-fiber texture” including moderate {111}<uvw>-oriented components, resulting in noticeable evolution of {111}<110> recrystallization texture during the solution treatment at a high temperature. The results of texture analysis and microstructural observation suggested that the low stored energy after asymmetric warm rolling, the high fraction of high angle boundaries with neighboring deformed matrices and the approximate 40° <111> orientation relationship with deformed matrices would strongly affect the evolution of {111}<110> recrystallization texture.

Abstract: The evolution of microstructure and texture due to recrystallization was investigated in cold rolled interstitial free (IF) steel. Samples taken from the cold band of a 0.07%Ti bearing IF steel with total cold rolling reduction of 75% were investigated by using optical microscopy, X-ray diffraction and electron back-scattered diffraction etc. The aim of this study was to obtain a real picture of the formation of the recrystallization texture of IF steel, which would contribute to proper texture control for improving deep drawability. The mechanism responsible for the evolution of texture is discussed experimentally from four aspects. First of all, the microstructure of partially annealed cold rolled specimen is obtained. The recrystallized grain form earlier in more darkly etched regions from the micrographs, which belong to the ND//<111> fiber components. In addition, the fractions of the {111}<110> and {111}<112> components increase slowly during the early stage of recrystallization, because the γ-fiber recrystallized texture is growing, while at the same time the γ-fiber deformed texture is being consumed. Moreover, The texture formation has been discussed taking into consideration of the stored energy and the misorientation between the orientation of the recrystallized grain and that of the surrounding deformed matrix. The work indicates that the recrystallized grains, which migrate into the deformed grains, are mainly with the high misorientation angles. The large percentage of the recrystallized grains, whose misorientation angles with deformed grains exceed 15°, are corresponding to the {111} transformation texture. Nucleation first starts at colonies that have the highest stored energy of deformation, which has the same orientation as the deformed grains. By analysis, the formation of recrystallization texture was well explained by oriented nucleation mechanism rather than by selective growth mechanism.

Abstract: The oriented-nucleation and oriented-growth for recrystallization (Rex) textures of electrodeposits, vapor deposits, and plastically deformed metallic materials have been discussed based on the strain-energy-release-maximization (SERM) model. When the Rex orientation predicted by the SERM model from major components of the deformation texture is the same as a minor component in the deformation texture that is calculated to be thermally stable by the SERM model, the calculated Rex orientation is sure to become the main component of the Rex texture. This implies that the oriented-nucleation and the oriented-growth affect the evolution of the Rex texture. For polycrystalline materials, the Rex orientation predicted by the SERM model is likely to be measured because heterogeneous nucleation can occur in grain boundaries even when shear bands are absent. In other words, the grain boundaries are unlikely to control the Rex texture and the oriented growth dominates the Rex texture.

Abstract: The formation of the Goss texture in electrical steels is one of the most distinct phenomena of texture research. Nevertheless, disregarding 60 years of research the mechanisms which let only Goss-oriented grains grow abnormally during a secondary recrystallisation annealing are still not completely understood. The present paper reviews some of the mechanisms of growth selection and oriented nucleation and discusses them in the light of observations made by the authors. We conclude that no mechanism proposed so far is able to explain all experimental observations. This points out the need for the search for a different mechanism.

Abstract: After primary recrystallization, on further annealing, abnormal grain growth occurred in ultra low carbon steel. Texture evolution was studied by comparing the orientations after complete secondary recrystallization, with on one hand the nuclei for abnormal grain growth and on the other hand the selective growth products of the primary recrystallized matrix. The influence of both mechanisms could be identified in the final texture.