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The Effect of Micro Segregation on the Observed Intensity in Thin-Film Microanalysis

Published online by Cambridge University Press:  06 March 2019

G. Judd  and
G. S. Ansell
G. Judd
Affiliation:
Rensselaer Polytechnic Institute Troy, New York
G. S. Ansell
Affiliation:
Rensselaer Polytechnic Institute Troy, New York
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Abstract

In the electron-probe microanalysis of thin alloy samples, particularly for areas which contain a high degree of solute segregation as are often obtained in extraction replicas or in electro chemically thinned foils, a correlation between the measured intensity and the sample microstructure has heen difficult to perform. The purpose of this study was to isolate the effect of micro segregation, i.e., segregation with respect to the beam size (∼2 μ) itself, on the characteristic intensity generated by a microvolurne. To accomplish this, a model system consisting of silver-powder particles (∼1 μ diameter) supported on an evaporated carbon film was investigated by using a thin-film microprobe accessory of an electron microscope (Hitachi HXA-1). The silver particles served as analogs to a highly concentrated segregation area, and the carbon film was analogous to the corresponding matrix. The simplicity of this system readily allowed for an analysis of the geometric positioning factor dependence of the generated intensity.

It was observed that the intensity measured for a given particle could vary by as much as 1000% depending only on the relative position of that particle within the electron beam. This variation was derived to be due to both the distribution of electrons within the beam and the amount of mass occupied by the particle at each distance from the beam center. A computer program was developed to perform the necessary calculation to predict the relative intensity as a function of position within the beam. These calculated intensities were found to compare favorably with the experimental measurements.

Type
Research Article
Information
Advances in X-Ray Analysis , Volume 11: Sixteenth Annual Conference on Applications of X-ray Analysis, August 9-11, 1967 , 1967 , pp. 306 - 315
Copyright
Copyright © International Centre for Diffraction Data 1967

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