Materials Science Forum Vols. 702-703

Abstract: Texture and microstructure of FSW joined Al and Cu sheets were investigated by means of electron backscatter diffraction (EBSD) technique. The analysis has revealed a strong texture evolution on both sides of the weld interface as well as a very complex microstructure. Grains were found to be fully recrystallized on both sides of the weld and with different average diameters at different specific zones of the weld.

Abstract: Electron Backscatter Diffraction measurement can provide much analytical information, such as the phase orientation or material identification. The “Quality” rating of the backscatter diffraction depends on the success rate of indexing. To achieve this, a deformation-free preparation is essential. In recent years most preparation methods have been optimized to contain on average only three to four sample preparation steps. The sample quality is excellent when reflected light microscopy is used. Due to the low information depth of the EBSD measurement (20-100nm), the standard method must be modified. The preparation method must remove the scratches and the underlying damage in order to obtain a high quality EBSD pattern. The optimization can be done by chemo-mechanical polishing, electrolytic polishing or vibratory polishing. Examples are used to show where the limits of the technologies are and to give helpful ‘Hints’ for EBSD sample preparation.

Abstract: The possible mechanisms concerning abnormal growth of Goss grains in grain oriented electrical steels were investigated. The density of inhibitor particles near sheet surface, where the Goss grains located, was lower than that in center layer before secondary recrystallization, and the grains near surface could grow more easily because of reduced pinning effect. Few Goss grains could survive the growth competition and reach the sheet surface, after which the inhibitor particles inside the Goss grains coarsened slower. The phenomenon resulted in easy growth of the Goss grains at the expense of smaller neighboring grains while they could hardly be consumed by larger neighboring grains during the high temperature secondary recrystallization. Very large final size of the Goss grains was then obtained. The mechanisms were discussed based on the hot rolling characteristics and the elastic anisotropy of the ferrite matrix.

Abstract: In order to verify the origin of Goss nuclei for secondary recrystallization in Fe-3%Si steel, the effect of cold-rolling direction on the secondary recrystallization was examined in this study. The cold-rolling direction was rotated through 0 ~ 90 degrees about the hot-rolling direction on normal direction axis of hot-rolled sheet. In spite of the different initial texture before cold rolling, the 88% cold rolled texture was formed by similar α and γ fiber regardless of the rotation of cold rolling direction. Likewise, regardless of the cold rolling direction, the primary recrystallized sheets had a similar texture. In particular, the area fraction of Goss component (tolerance angle within 15º) in the primary recrystallized sheets was increased in the cold rolling condition of rotating through 60, 90 degrees from the hot rolling direction. After high temperature annealing at 1200°C, the secondary recrystallized grain was fully evolved in the all conditions. The sharpness of Goss texture in secondary recrystallized sheet was decreased as increasing the rotation angle of cold rolling direction.

Abstract: Non-oriented grain type electrical steels are used mainly in electrical rotating machines such as motors and compressors, in which the magnetization direction rotates 360 ° every cycle while remaining in the plane of the plate. The performance of these devices is affected by crystallographic texture of electrical steels due to strong anisotropy of magnetic properties. The electrical steel is supplied in the form of plates which are processed by cold rolling and subsequent annealing. Both, cold rolling and annealing directly influence the formation of crystallographic texture components. During annealing, recrystallization occurs, and this phenomenon gives rise to changes in texture that influences the quality of the final product and its application. Several works have been published in the study of the evolution of crystallographic texture and grain size in this type of electrical steel. In this work, samples have been taken in industrial conditions at various temperatures during the annealing in a coil box. Electrical steel samples cold rolled with reductions of 50% and 70% in thickness were removed during the process of annealing, and the evolution of texture with increasing temperature was studied. Aspects related to recrystallization, grain size and the evolution of texture and magnetic properties were discussed. Texture and recrystallization were studied by X-ray diffraction and electron backscatter diffraction (EBSD). The magnetic properties were measured in a vibrating sample magnetometer.

Abstract: In silicon steels, interaction of grain boundaries with particles occurs in a selective way. Currently, it is very difficult to include this preferential interaction directly in the classical simulation models. A new approach of grain growth simulation based on the concept of curvature-driven migration of the grain boundaries in the presence of particles has been used to study the abnormal grain growth (AGG) in Fe-3%Si alloy.

Abstract: In this study, the commercial purity Al/Cu plates were bonded through the explosive welding process. The SEM/EBSD local orientation measurements were conducted to consider the changes in the microstructure and the development of texture gradients for the applied explosive loading. A particular attention was paid to the texture changes across the interface. The detailed local orientation measurements show that the ultra-fine grained layers are formed close to the bonding zone. The layers were characterized by the copper-type rolling texture components. The interface was outlined by a characteristic sharp transition between the two materials. However, in some places, local melted zones were also encountered, mainly in the front slope of the waves.

Abstract: The extended band structures of cold-rolled high Cr steel sheets are recrystallization resistant, and tend to become the so-called grain colony as a recovered state. It is shown that a novel approach involving strain-path change by introducing one-pass ECAP prior to cold rolling facilitated recrystallization. Indeed, recrystallization temperature was reduced by 100 °C, compared with cold rolling alone imposing the same equivalent strain. Dense deformation bands introduced during ECAP perturbed the banded structures and enhanced the recrystallization at final annealing.

Abstract: The changes in crystallographic texture are investigated during recrystallization in 5182 and 6016 aluminum alloys, which were subjected to various cold rolling reductions. In the current study, the texture varieties in the recrystallized materials are conditioned by both the material’s chemistry and the applied rolling strain. The presence of large constituent particles produces strain heterogeneities during cold rolling which causes a specific texture development. The development of recrystallization textures is discussed based on experimental data and results of crystal plasticity simulations. A recrystallization model based on nucleation and growth selection is presented. The driving force for nucleation was accounted for by applying continuum mechanics crystal plasticity models. For the modeling of the strain heterogeneities around hard undeformable particle a FE-code was used.

Abstract: A two dimensional probabilistic cellular automata model is used to simulate primary static recrystallization of interstitial free (IF) steel. The present study is to investigate the effect of curvature-driven pressure that is induced by protrusions/retrusions of recrystallization fronts on the microstructural and textural evolution during recrystallization. It was found that local interface migration of protrusions/retrusions of recrystallization fronts could significantly affect the kinetics, grain morphology and annealing texture according to the present investigation.