Materials Science Forum Vols. 495-497

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 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: Free-standing line patterns of Cu and Ni were manufactured by electrochemical deposition into lithographically prepared patterns. Electrodeposition was carried out on top of a highly <111> oriented Au-layer physically vapor deposited on glass. Quantitative texture analysis carried out by means of X-ray diffraction for both the substrate layer and the electrodeposits yielded experimental evidence for epitaxy between Cu and Au. An orientation relation between film and substrate was discussed with respect to various concepts of epitaxy. While the conventional mode of epitaxy fails for the Cu-Au-system, it is shown that the experimentally observed orientation relation can be conceived as a 30º rotation of Cu (111) grown on Au (111) (rotational epitaxy).

Abstract: Texture transition in silver introduced by the addition of 10 at% Pd alloying element was analyzed in this study. Experimental results show that the dependence of rolling texture on rolling reduction in thickness rather than on rolling temperature has been mostly detected, and the recrystallization texture transition process in pure silver is so strongly influenced by the addition of alloying element palladium that the final stable state of recrystallization texture has been changed from Brass {011}<211> orientation to Copper {112}<111> orientation. The single cube {001}<100> recrystallization texture in warm rolled silver, Brass {011}<211> recrystallization texture in room-temperature rolled silver, and Copper {112}<111> recrystallization texture in room-temperature rolled or warm rolled Ag-10 at% Pd alloy have been successfully developed for the fabrication of metallic substrates suitable for high-temperature superconducting tapes.

Abstract: In this paper we report a study using fully automated EBSP orientation measurements on the texture and microstructure of fully processed Bi-2223 tapes produced by the powder-in-tube method. For the automated analysis a new unit cell describing the quasi-tetragonal Bi-2223 phase has been developed. The texture data confirm that a strong fibre texture is produced during processing, with the c-axis of the Bi2223 plates parallel to the tape normal direction. Quantitative analysis suggests that the orientation density along the fibre texture is close to random. In contrast the distribution of misorientations shows significant correlations between the orientations, and is skewed towards low misorientation angles. A more detailed investigation reveals that the structure consists of colonies of plates, with low angle misorientations within each colony. Analysis of the rotation axes shows some differences as a function of misorientation angle.

Abstract: The magnetic parameters of steel depend on the mutual orientation of the applied magnetic field, the (applied) stress and the crystalline structure. The magnetic anisotropy can be modeled in terms of the magneto-elastic and magneto-crystalline energy distributions. By investigation of the magnetic anisotropic behaviour of steels with respect to stress, a rapid, nondestructive and possibly non-contact measurement of the residual stress can be devised that can find application in manufacturing, machining, forming and life-time assessment of steel and steel components. Reliability, robustness and versatility will constitute the main challenges to further develop these techniques for common industrial applications.

Abstract: The yield strength was investigated in a prestrained and baked bake-hardenable sheet steel, which can increase the dent-resistance of exterior automotive body panels. Instead of a standard bake-hardenability test in which the final tensile test is in the same direction as prestrain, the strain-path effect in denting of stamped and paint-baked panels was examined by changing the direction of final tensile tests in uniaxially prestrained and baked samples. The prestrained samples showed the maximum of 0.2% proof stress at 45° to the prestrain axis and the minimum at 90°. Baking raised the minimums at 0° and 90° so that the anisotropy decreases. Furthermore, the strain path changes were characterized by a scalar product of previous and current strain-rate mode tensors. By regarding this parameter as the degree of reactivation of slip systems, the anisotropy observed after prestraining and baking was microscopically explained from the viewpoints of residual stress, crystal plasticity, and dislocation pinning.

Abstract: This investigation aimed at the understanding of texture development during r-value determination by uniaxial tensile testing. Special emphasis was given to examine the texture evolution in the deformation zone of the tensile test specimen during mechanical r-value determination. The textures of different sheet steel grades were investigated in different deformation stages by the orientation distribution function (ODF) and mechanical testing.

Abstract: The toughness anisotropy in steel plates (0.08%C, 1.52%Mn, 0.3%Si, 0.055%Nb and 0.078%V) was studied in relation to the crystallographic texture and microstructural anisotropy of the material. The plates, with a ferrite –pearlite microstructure, were obtained by hot rolling in a laboratory reversible rolling mill to 66% reduction with the final rolling pass in the two-phase (g/a) domain followed by accelerated cooling to 570°C and subsequent slow cooling to room temperature (coiling simulation). Standard size Charpy samples with their long axis oriented at 0, 22.5, 45, 67.5 and 90° with respect to the rolling direction of the plate were tested at different temperatures varying from +20°C to –80°C. Microstructures and textures of the plates were studied by means of orientation scanning electron microscopy and XRD. A specific toughness anisotropy profile was observed which could not be correlated to the crystallographic texture of the plates, which all displayed very weak, almost random transformation type textures with a maximum intensity of approximately 2x random. Therefore, it was investigated whether the toughness anisotropy might be related to the microstructural anisotropy rather than to the crystallographic texture. The study of the grain size distribution in differently oriented sections together with the distribution of the pearlite zones in these sections revealed that the directional changes in the toughness could be successfully associated to these parameters. A significant increase in the absorbed impact energy from 140J to 270J, together with a remarkable decrease of the toughness anisotropy at room temperature, was observed after annealing the hot rolled samples at an intercritical temperature followed by an isothermal treatment in the low bainite region. The observed effect was explained by the replacement of the pearlite constituents by lower bainite in the grain boundary regions which produced a local strengthening of grain boundaries.

Abstract: Under consideration is an allowance for internal grain-scaled stresses in the evaluation of residual macroscopic stress in highly textured polycrystals. The grain-scaled stresses have been evaluated with two micromechanical models: (a) a simplified model developed for a very strong <110> fiber texture and suggesting the corresponding peculiarity of slip pattern in constitutive crystals, and (b) a full-constraint model allowing for accommodation nature of the multi-slip pattern in these crystals. Both models satisfactorily predict the position and relative intensity of the nonlinearities of d{hkl}-sin2y curve. The former model, by treating magnitude of grain-scaled stresses as a fitting parameter, provides better correspondence to experimental data. The latter model, free of fitting parameters, overestimates the grain-scaled stresses, and, consequently, the oscillations of d{hkl}-sin2y curve.