Papers by Keyword: Orientation Image Microscopy (OIM)

Abstract: An Fe-2%Si alloy, which was designed for electromagnetic applications was submitted to a series of plane strain compression (PSC) tests with reductions of 25, 35 and 75% at temperatures varying from 800 to 1,100°C and at a constant engineering strain rate corresponding to a constant cross velocity of 20 mm/s. The initial structure of the material displayed nearly equi-axed grains with an average size of 80 μm. The as-received texture was characterised by a nearly random cube fibre (<100>//ND) with a relatively weak maximum on the rotated cube component ({001}<110>). After deformation the samples were water quenched in order to avoid post-process static recrystallization events. The microstructures were analysed by orientation imaging microscopy (OIM) revealing that the zone of PSC was restricted to the central layers of the sample but minimally covering 50% of the sample thickness. After deformation at 800°C the conventional lamellar deformation structures were observed on the sections perpendicular to the transverse direction of PSC. At higher deformation temperatures the structure was of a bimodal nature consisting of lamellar deformation bands and equi-axed small grains. The volume fraction of these small equi-axed grains increased from 19.9% after 75%reduction at 800°C to 67.8% after 75% reduction at 1.100°C. After 75% reduction the equi-axed grains exhibited an average size of 10 μm which represents a strong grain refinement with respect to the initial size of 80 μm prior to PSC. Ferrite Silicon steels undergo extensive dynamic recovery during hot working. Dynamic recrystallization (DRX), though, has not yet been reported for these alloys although the present data suggest that a DRX mechanism might be responsible for the remarkable grain refinement after relatively low amounts of strain applied at high temperatures.

Abstract: The article takes into account various factors which effect the texture evolution in the Cu lines. We propose here an explanation for the formation of {111}<110> and {111}<112> texture in the Cu lines. The explicit role of principal stresses, shear stresses and dislocations is discussed. The influence of line spacing on strength of the {111}<110> and {111}<112> texture components is also demonstrated in relation to the dislocation density.

Abstract: In the present paper we report the texture and microstructure dependence of electromigration damage in Cu interconnects. This was made possible by ncorporating a sophisticated set of instrumentation within the SEM which enabled in-situ monitoring of the electromigration defects. The electron backscatter diffraction (EBSD) maps were obtained before and after the completion of the electromigration tests. Thus, by comparing the maps before and after the failure it was possible to associate the texture and microstructure with both failure sites - voids and hillocks. Results from lines down to 130 nm are included and orientation dependence of the defects is discussed.

Abstract: The influence of current density and temperature on the macrotexture, the orientation and size of grains, and the corrosion resistance of tin deposits was studied. Tin coatings with two different textures, (100) and (301) fiber textures were produced by electrodeposition at 20°C by varying current density. At a lower current density of 100A/m2, (301) fibre was obtained. At the current densities of 100 and up to 400 A/m2, only (100) fibre texture was observed. An increase in current density leads to a decrease in grain size. At the same current density, the grain size of tin coatings increases with increased temperature. The influence of temperature (20, 40, 60 and 80 °C) on texture is relatively negligible. The corrosion resistance of tin coatings increases with a decrease in grain size. The corrosion resistance of tin coating with (301) fibre is higher than that of tin coating with (100) fibre texture. The results suggest that texture and microstructure play an important role in controlling corrosion rate of tin based coatings.

Abstract: Textural changes of Cu interconnects having a different line width were investigated after annealing. Texture was measured by XRD (x-ray diffraction) at different depth of the interconnect line and on the surface of interconnects using EBSD (electron backscattered diffraction) techniques. To analyze the relationship between the stress distribution and textural evolution observed in the different samples, the stresses were calculated for the different line width at 200°C using FEM (finite element modeling) along the width and depth of the line. In this investigation, it was found that the inhomogeneity of stress distribution in Cu interconnects is an important factor necessary for understanding textural transformation during annealing. Textural evolution in damascene interconnects lines during annealing is discussed, based on the state of stress in Cu electrodeposits.

Abstract: This work presents the results of a study on textural and microstructural inhomogeneities that develop during annealing of heavily drawn Oxygen free high conducting (OFHC) copper wire. The wire was drawn at room temperature to a true strain of 2.31 and isothermally annealed at 750°C for annealing times ranging from 10s to 1hr. The inhomogeneity of microstructure across the wire was clearly visible as three distinct concentric regions, which were classified as: the inner core, the mid section, and the outer surface. Two texture transitions were observed. At shorter annealing time, recrystallization which originated from the mid section, resulted into a strong<100>+weak<111> duplex fiber texture. However, prolonged annealing gave rise to abnormal grain-growth that proceed from the mid section to the outer surfaces with a dominant <111> fiber component at the mid and inner region, and mixed components of <111>, <100>, and <112> at the outer surfaces.

Abstract: The mechanical processing of metals results often in development of preferred orientation of grains or texture. On the other hand, the orientations of grains have a significant effect on the friction and wear behaviour of materials in contact. The objective of this investigation was to determine the crystallographic anisotropy of the coefficient of friction. Medium carbon steel AISI 1045 were selected as the substrate material. Automated orientation imaging analysis system (OIM) was used to identify orientations of grains in polycrystalline specimens. Micro-friction tests were carried out using a Tribocope, a combination of nano-mechanical probe and atomic force microscope with an electrochemical cell. The micro friction tests were performed along different crystallographic directions inside different grains.The obtained results have shown that the coefficient of friction for individual grains depends on crystallographic orientation, and that the coefficient of friction for higher atomic density planes is lower than that for lower atomic density planes.

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: The improvement of the mechanical behaviour of high performance steels brings about a renewed interest for the work hardening rate resulting from deformation-induced martensitic transformation or mechanical twinning. Even if these mechanisms are known for quite a long time, the deformation – transformation interactions that they induce is not yet fully characterised and understood. This study aims at characterising the microstructure evolution of a Fe-Mn steel grade during straining thanks to TEM and high resolution OIM. Particular patterns of austenite – e and a’ martensite are found.