Materials Science Forum Vols. 495-497

Abstract: The influence of the oxygen-content, the rolling method, the annealing method and the annealing temperature on the texture in silver have been studied. The results show that low oxygen-content in original material, annealing at a temperature higher than 700ı and annealing in an atmosphere such as inert gas, air or pure oxygen are beneficial to obtain the {110}<110> component. Textured Ag substrate in which the main components is {110}<110> has been obtained. The mechanism of texture-forming is studied using electron back-scattered diffraction (EBSD) method.

Abstract: We find that a severely rolled FeCo alloy has anomalous enhancement of the rotated-cube {100}<011> texture component and a decrease of the {111} components after annealing, which is contrast to the recrystallization behaviors reported in traditional BCC metals and alloys. The local texture measurements show that two kinds of grains with obviously different orientations, i.e. {100} and {111}, are heterogeneously distributed in the deformed specimen and the migration of high-angle grain boundaries is observed after annealing in the disordering temperature region.

Abstract: Texture and microstructure evolution during cold rolling of binary Ni3Al single crystals were studied as a function of the initial crystal orientations. Cold rolling behavior of the single crystals is strongly dependent on the initial crystal orientations, especially on the initial rolling direction (RD). Macroscopic texture evolutions for binary Ni3Al single crystals with the initial RD close to <001> are characterized as development of dual {110}<¯112> texture above 90% cold reduction and the banded structure formation. Microstructure observations reveal the extensive formation and accumulation of the planar defects including the stacking faults and the planes where the localized shear deformations occurs, which must be responsible for the observed anisotropic cold rolling behavior of Ni3Al single crystals.

Abstract: Polycrystalline samples of NiAl have been deformed in torsion in the temperature range 800K – 1300K. Deformation is accompanied by dynamic recrystallization, which with increasing temperature changes from continuous to discontinuous mode. Emphasis was put on the occurrence of continuous dynamic recrystallization, which will be discussed with respect to texture and microstructure.

Abstract: In electroformed pure Ni and Fe-Ni alloys with nanometer-sized crystallites, grain growth that takes place during annealing results in a common texture change. With regard to the macrotextures, the as-deposited textures were of fibre-type characterized by strong <100>//ND and weak <111>//ND components, and the texture development due to grain growth was defined by strong <111>//ND fibre texture with the minor <100>//ND components. It was clarified by means of the microtexture analysis that abnormal growth of the <111>//ND grains occurs in the early stages of grain growth. The possible effects of the abnormal grain growth on the texture evolution have been discussed in terms of the orientation dependence of energy density.

Abstract: Optimized conditions of hot and cold rolling followed by annealing can result in a balance between recrystallization and rolling textures in order to reduce the planar anisotropy of brass sheets. In this work, the effect of finish rolling temperature, cold reduction and annealing temperature on texture development has been investigated. It is shown that uniform deformation at higher finishing temperature is responsible of formation of a severe Cube and G texture components. In contrast, mechanical twinnings are widely formed at low finishing temperatures. There is also a direct relation between the intensity of Cube component and the amount of cold reduction.

Abstract: Copper single crystals of {110}<001> crystallographic orientation were cold rolled to a true strain of 1.4. Specimens were cut from the as-deformed crystals with all surfaces mechanically ground and deep-etched in concentrated nitric acid to minimise the likelihood of surface nucleation of recrystallized grains during subsequent annealing. The early stages of static recovery were studied by annealing specimens at 300 oC. The crystallographic features of the deformed and annealed microstructures were determined by high resolution electron backscatter diffraction. It was observed that deformation was homogeneous with the microstructure in ND-RD plane exhibiting two complementary sets of intersecting bands at ~+ 35o to ND. Along these bands and in the microstructure, in general, there was an overall spread in orientation about ND towards {110}<112>. However, the orientation spread along these bands was cyclic, that is, sinusoidal orientation gradients were generated about ND with amplitude of up to 20o and wavelength 5-10 µm. Annealing resulted in the preferred growth of cells that have orientations at the edge of the orientation spread of the deformation substructure. This localized coarsening of the microstructure is similar to the discontinuous subgrain growth observed in {110}<001> oriented Al single crystals and indicates that discontinuous subgrain (cellular) growth can also occur in metals of lower stacking fault energy.

Abstract: Anisotropic deformation behavior of single crystalline Ni3Al-base intermetallic compounds, including Ni3Al single-phase and Ni/Ni3Al two-phase alloys, was systematically studied by the plane strain compression tests. Plastic flow behavior of single phase Ni3Al is strongly dependent on the initial crystal orientation and the flow stress becomes higher with increasing the numbers of the operative slip planes. In the case of the Ni/Ni3Al two phase alloys, the flow behavior is found to be divided into two stages. Such flow behavior is considered to be closely related to the difference in the deformation behavior between Ni solid solution and Ni3Al precipitates.

Abstract: The present work reports on the results obtained on equal channel angular extrusion experiments (ECAE) done on a laboratory-cast Al-4%Cu alloy, in the T4 condition, and the use of Polycrystalline-FEM simulations to assist in the interpretation of the experiments. The experimental setup consists on a die of approximately 15 x 15 mm2 sections intersecting at 120o. Deformation at room temperature consisted of up to 5 passes with no rotation between passes. After each extrusion pass, the samples were cut from the deformed billet along planes parallel to the extrusion direction and the preferential orientations were measured on surface and middle layers. Three pole figures, (111), (200) and (220) were measured by conventional x-ray diffraction techniques and used for Orientation Distribution Function calculation and analysis. In addition tensile tests and optical microscopy have been performed in each sample to provide a good estimation of the parameters that enter in the modeling process. A finite element code specially developed to model large deformation processes (Forge3Ò) was used with tetrahedral elements and an elastic-viscoplastic material model to investigate the influence of the different strain paths sustained by different areas of the samples. The calculated distribution of deformations agrees well with the theoretical result. The simulation was used to assist in the selection of sample-cutting procedures for texture measurements and to provide the strain paths needed for self-consistent polycrystal modeling of texture development.

Abstract: The paper represents results of computer modeling of texture formation in pure copper subjected to severe plastic deformation (SPD) realized by equal channel angular pressing (ECAP). Several polycrystalline models, namely the Taylor model, Sachs model, and self-consistent viscous plastic (VPSC) model, were applied and their predictions of texture evolution for different routes and number of ECAP passes were compared. For these calculations, simple shear deformation was used for the deformation realized by ECAP. Using the VPSC model, a single ECAP pass was revisited, but employing a 3D model of material flow, conducted by the variation-difference method, for the ECAP deformation. The influence of the inner and outer radii at the channel intersection and the friction coefficient on the homogeneity of the texture development in the cross section of the bulk ingot was investigated.