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The deformation behavior of BCC metals is being investigated by x-ray microdiffraction measurements (mu XRD) for the purpose of characterizing the dislocation structure that results from uniaxial compression experiments. The high brilliance synchrotron source at the Advanced Light Source (Lawrence Berkeley National Lab) and the micron resolution of the focusing optics allow for the mapping of Laue diffraction patterns across a sample. These measurements are then analyzed in order to map the distribution of residual stresses in the crystal. An important findingis the observation of Laue spot "streaking," which indicates localized rotations in the lattice.These may represent an accumulation of same-sign dislocations. Theoretical modeling of the diffraction response for various slip systems is presented, and compared to experimental data. Preliminary results include orientation maps from a highly strained Ta bicrystal and a less highly strained Mo single crystal. The orientation maps of the bicrystal indicate a cell-like structure of dense dislocation walls. This deformation structure is consistent with previous OIM studies of the same crystal. The results suggest that mu XRD may be a particularly useful tool for microscale studies of deformation patterns in a multi-scale investigation of the mechanisms of deformation that ranges from macroscopic deformation tests to high resolution TEM studies of dislocation structures.

In the present paper the evolution of the dislocation structure during electromigration in different regions along the Al(Cu) interconnect line is considered. It is shown that plastic deformation increases in the regions close to cathode end of the interconnect line. A coupling between the dissolution, growth and re-precipitation of Al2Cu precipitates and the electromigration-induced plastic deformation of grains in interconnects is observed. Possible mechanism of the Cu doping effect on the improved electromigration resistance of the Al(Cu) interconnects is discussed.

Electromigration during accelerated testing can induce large scale plastic deformation in Al interconnect lines as recently revealed by the white beam scanning X-ray microdiffraction. In the present paper, we provide a first quantitative analysis of the dislocation structure generated in individual micron-sized Al grains during an in-situ electromigration experiment. Laue reflections from individual interconnect grains show pronounced streaking after electric current flow. We demonstrate that the evolution of the dislocation structure during electromigration is highly inhomogeneous and results in the formation of unpaired randomly distributed dislocations as well as geometrically necessary dislocation boundaries. Approximately half of all unpaired dislocations are grouped within the walls. The misorientation created by each boundary and density of unpaired individual dislocations is determined.

The distribution of strain, defects, and crystallographic tilt in uncoalesced GaN layers grown by maskless pendeo-epitaxy are determined by using polychromatic x-ray microdiffraction, high-resolution monochromatic x-ray diffraction, and finite element simulations. The width-to-height ratio of the etched columns of GaN from which occurred the lateral growth of the wings are the important material parameter.

The spatial distribution of strain, misfit and threading dislocations, and crystallographic orientation in uncoalesced GaN layers grown on Si(111) substrates by maskless cantilever epitaxy is studied. The measurements revealed that the free-hanging wings are tilted upward at room temperature in the direction perpendicular to the stripes.

Dislocation structure changes of Ni-based single crystal superalloy during impulse heating up to the melting temperature are studied using polychromatic microbeam synchrotron diffraction together with electron and optical microscopy. It is found that the maximum value of the thermal gradient is observed in the heat affected zone (HAZ) near the fusion line.

Analysis of the dislocation structure in the heat affected zone (HAZ) that will enable one to define the extent of a true HAZ and improve physical processes taking place during welding and weld cooling of Ni-based alloys is discussed. Changes occurred during spot welding of single-crystal Ni-based superalloy TSM-75 is observed.

The way to quantitatively determine the dislocation structure of single crystals and polycrystals with plastic deformation is shown. The technique is applied to interpret the complicated plastic-elastic field in an iridium weld sample.