Abstract
Many material properties are determined by the segregation (or lack of it!) of atoms of trace elements to boundaries, including, for example, the strength, electrical conductivity, dielectric constant, and diffusion properties. Many scientists are therefore interested in measurements of the segregation, and have found the field-emission scanning transmission electron microscope to be an invaluable tool.There are two cases to be differentiated. In the first, typified by sensitization in stainless steels, the width of the segregation or depletion zone is large compared with the diameter of the electron probe and the beam broadening. In the second, the reverse is true, the beam diameter and/or the beam broadening is large compared with the extent of the segregation. While the first case is certainly of interest, this paper will be concerned solely with the second.The earliest attempts at detecting grain boundary segregation by AEM were made by Doig et. al., studying tin segregation in iron alloys in a 100kV microscope with a tungsten-hairpin electron gun.
Publisher
Cambridge University Press (CUP)
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1. 9. The author acknowledges major support for this work from the National Science Foundation, through the Center for Materials Science and Engineering at MIT, under Block grant # DMR90-22933
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