9700674 Cohen The local atomic arrangements at surfaces of alloys is the major theme of this research. Of particular interest is how changes in the environment, such as reconstruction or interplanar spacing normal to the surface or segregation ,affect phase transitions such as ordering and clustering. Strain plays an important role in such reactions, and a beam line at Argonne Laboratory's new Synchrotron (the Advanced Photon Source, or APS) is used employing an X-ray glancing incidence technique. The X-rays sample a shallow range of depths producing diffuse scattering that is analyzed in a position-sensitive detector. From these data short range order parameters and distortions are obtained. Samples include single crystals of aluminum alloys that are prepared featuring a few facets with different possible relaxations. After heat treatment to produce zones, concentration profiles vs. depth are determined and Auger electron spectroscopy and low energy electron diffraction are used to look for evidence of surface reconstruction or relaxation. Diffuse scattering is measured vs. depth, and the surface structures and displacements modeled and compared to the bulk structure. %%% An understanding of surface structure aids in analysis of related phenomena, such as corrosion of metal alloys and crack initiation. ***
