Local Atomic Arrangements at Alloy Surfaces

小行星9700674 合金表面原子的局域排列是本研究的主要内容。 特别感兴趣的是如何在环境中的变化，如重建或晶面间距垂直于表面或偏析，影响相变，如排序和集群。 应变在这种反应中起着重要的作用，阿贡实验室的新同步加速器（高级光子源，或APS）的光束线采用X射线掠入射技术。 X射线对产生漫散射的浅深度范围进行采样，在位置敏感探测器中进行分析。 从这些数据中获得的短程有序参数和失真。 样品包括铝合金的单晶，其制备具有不同可能弛豫的几个小面。 在热处理以产生区域之后，确定浓度分布与深度，并且使用俄歇电子能谱和低能电子衍射来寻找表面重建或松弛的证据。 测量漫散射与深度的关系，对表面结构和位移进行建模并与体结构进行比较。 对表面结构的理解有助于分析相关现象，如金属合金的腐蚀和裂纹的产生。 ***

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. ***