Solid State Phenomena Vol. 105

Abstract: The change of the deformation path leads to destabilization of the substructure and affects the texture of the deformed metal. The observed changes of texture and microstructure are, as a rule, significant and their characteristics depend on the geometry of the deformation process. Previous investigations on copper (and copper alloy) samples after deformation by rolling and channel-die compression were based on X-ray pole figure measurements and on observations in the light microscope. Hereby only global texture and structural characteristics have been obtained. The present study is mainly based on measurements of individual crystal orientations performed by ACOM (Automated Crystal Orientation Measurement, “Automated EBSD”) in the SEM which enables a precise local analysis of the investigated phenomena. For the channel-die experiments, (1 1 2)[1 1 -1] and (1 1 2)[1 -1 0] oriented copper single crystals have been used. After pre-deformation, a second deformation step has been carried out in transverse direction. The {1 1 2}<1 1 0> orientations are destabilized by channel-die compression, and clusters of layers develop which are composed of complementary {1 1 0}<1 1 2> components. The deformation process in polycrystalline sheets after rotating the rolling direction leads again to a distinct disintegration of the microstructure and destabilization of the b fiber. This process of microstructure reorganization after pre-deformation is fast and of high dynamics.

Abstract: Copper of 4N purity was deformed at room temperature by equal channel angular pressing (ECAP) using three passes of route A. The local microstructure and texture were investigated by orientation imaging microscopy and high-energy synchrotron radiation, respectively. The microstructure consists of elongated grains which are inclined to the extrusion direction. The texture is characterized by typical shear components of fcc metals which deviate from their ideal positions. The inclination of the grain long axis and the texture components with respect to the extrusion direction depends on the distance from the top of the extruded bar and changes from pass to pass. Reasons for the texture gradient are discussed.

Abstract: Texture and microstructure were investigated after 1 pass equal channel angular extrusion (ECAE) of a single crystal cube oriented Ni billet. Neutron and X-ray diffraction were used to determine global and local textures, respectively. To investigate the fine scale microstructural features EBSD was used. Substantial variations in texture and microstructure resulting from different efficiencies in the shearing process were locally recorded through the billet height.

Abstract: The orientation distribution functions of conventionally prepared and pre-deformed copper and aluminium up to ı = 7.2 by the Equal-Channel Angular Pressing mode C, and then cold rolled up to 95 % area reduction have been analyzed in the paper. The rolling texture of conventionally prepared coarse-grained copper was characterized by {011}<3-11> component, whereas that of small-grained copper was characterized by {351}<1-12>. However, both components were present in copper pre-deformed up to ı = 7.2 by ECAP technique. In the ECAP pre-deformed aluminium the perfecting of the {113}<12-1> component of the rolling texture followed the increase of deformation. The texture has been discussed in relation with mechanical properties and structure observations.

Abstract: FCC metals with different stacking fault energy (SFE), namely Al, Cu and Ag have been investigated for the evolution of crystallographic texture during ECAE deformation using Route A. Different materials with different SFE result in their characteristic textures. The results have been analysed on the basis of microstructural features and related established concepts on texture evolution in FCC metals during other deformation modes.

Abstract: Aluminum of 5N purity has been deformed at room temperature by equal channel angular pressing using three passes of route A. The microstructure and texture have been investigated by electron back-scattering and neutron diffraction. The microstructure from the first pass on is totally dynamically recrystallized. The recrystallization texture consists of an oblique cube component. The oblate grains and the cube texture are anticlockwise rotated about the transverse direction. The inclination with respect to the extrusion direction depends on the distance from the top of the extruded bar and changes from pass to pass. The mechanism of ormation of the recrystallization microstructure and texture is discussed.

Abstract: FCC metals with different stacking fault energy (SFE), namely Al, Cu and Ag have been investigated for the evolution of crystallographic texture during ECAE deformation using Route A. Different materials with different SFE result in their characteristic textures. The results have been analysed on the basis of microstructural features and related established concepts on texture evolution in FCC metals during other deformation modes.

Abstract: In-situ SEM shearing tests were performed on samples from the heavily cold rolled (Extrahard) aluminium alloys, where the parallelepiped test sample was cut as to let shear direction (SD) have an angle α with the rolling direction (RD). This shear angle ranges from 0o to 165o with an interval of 15o. These include three heavily cold rolled non heat-treatable aluminium alloys AA1200, AA3004 and AA5182. During these tests, strain localization (macro-shearbands) was bserved. This phenomenon is found to be anisotropic and depends on the angle α. The strain localization or macro-shearbands are believed to be related with strain softening, where the flow stress decreases with strain. According to the crystal plastic theory, the strain softening is considered as resulting from the joint effects of texture and evolution of microstructure, in particular the dislocation patterns. Focusing on texture softening, simple and advanced Taylor type micro-mechanical simulations (Full-constraint Taylor (FC Taylor) and Advanced Lamel models (Alamel)) are performed to calculate the texture and average Taylor factor evolution with the increment of shear strain, on the basis of the measured rolling textures. After the simulations, the shear strain at which texture softening happens is recorded for each alloy and each shear angle. For alloys AA3004 and AA5182, it is found the texture-softening trend is similar to the experimental observations, which showed that the strain localization starts at smaller strains at shear angles of around 30-60o and 120-150o, finally leading to early failure. On the contrary, for alloy AA1200, the calculated average Taylor factor evolution does not resemble the flow behaviour. Furthermore the conclusions for alloys AA3004 and AA5182 are only qualitative, as the value of texture-softening strains predicted by simulation seems different from the observations. This shows that the importance of other effects such as possible microstructural softening mechanisms, especially the one due to the change of strain path (rolling/shear). Then for future models, it will be necessary to incorporate both the texture effects and microstructural effects comprehensively in order to precisely predict the strain localization behaviour of materials.

Abstract: This work deals with early results obtained in numerical simulation of the skin-pass of zinc coated steel sheets. First, the streamline model and its adaptation to the case of the temper rolling of coated steel sheets are detailed. Second, the influence of various parameters of the rolling process on the strain and stress fields in the sheet is numerically calculated.

Abstract: Determination of the domain textures in many lead zirconate titanate (PZT) piezoelectrics can be complicated by the presence of second phases, internal strains and small differences in lattice parameters for the commonly used 002 and 200:020 peaks. The domain texture is influenced by the applied polarization necessary for these materials to demonstrate piezoelectricity. In this paper we explore the use of 022:202 and 220 peaks for evaluating the domain textures and helping resolve the complexities of texture analysis in the presence of multiple phases. The two materials explored in this paper include a nominally single phase tetragonal PZT material and a mixed phase tetragonal-monoclinic lead magnesium niobate (PMN)-PZT alloy.