Li Chunfei, Williams David B
Department of Materials Science and Engineering, Lehigh University, Bethlehem, PA 18015, USA.
Micron. 2003;34(3-5):199-209. doi: 10.1016/s0968-4328(03)00026-x.
Analytical Electron Microscopy (AEM) has brought significant progress in the study of grain-boundary segregation. Using X-ray energy-dispersive spectrometry (XEDS) in the AEM, elemental segregation information can be related to the crystallographic character of the same boundary via conventional Transmission Electron Microscope (TEM) diffraction techniques. While significant efforts have been made to improve XEDS analysis of sub-nanometer segregation layers, the methods for crystallographic characterization of grain boundaries have remained the same for several decades and labor-intensive processes. Recently, a method termed Automated Crystallography for TEM (ACT) was developed, which automates crystallographic characterization of grains under TEM observation. In the present work, we combine ACT and X-ray mapping via EDS in AEM for the study of Sb grain-boundary segregation in a rapidly solidified Cu-0.08 wt % Sb alloy. In contrast with previous reports, a large degree of anisotropy in Sb segregation level between different boundaries is found. ACT results suggest that one of the several grain boundaries observed with no detectable Sb segregation is very close to a Sigma 3 coincidence-site lattice structure. The reason for the observed anisotropy in the present alloy is discussed, based upon McLean's theory of segregation.
分析电子显微镜（AEM）在晶界偏析研究方面取得了重大进展。在AEM中使用X射线能量色散谱（XEDS），通过传统的透射电子显微镜（TEM）衍射技术，可以将元素偏析信息与同一晶界的晶体学特征联系起来。虽然人们已经做出了巨大努力来改进对亚纳米偏析层的XEDS分析，但几十年来，晶界晶体学表征方法一直没有变化，且过程繁琐。最近，开发了一种称为TEM自动晶体学（ACT）的方法，该方法可在TEM观察下自动对晶粒进行晶体学表征。在本工作中，我们将ACT与AEM中通过能谱进行的X射线映射相结合，用于研究快速凝固的Cu-0.08 wt% Sb合金中的Sb晶界偏析。与之前的报道不同，我们发现不同晶界之间的Sb偏析水平存在很大程度的各向异性。ACT结果表明，观察到的几个没有可检测到的Sb偏析的晶界之一非常接近Sigma 3重合点阵结构。基于麦克林偏析理论，讨论了本合金中观察到的各向异性的原因。
