Metallurgical Applications of X-Ray Fluorescent Analysis

Abstract

Techniques are described for fluorescent analysis using an x-ray Geiger counter goniometer. Consideration is given to the influence of potential variations, specimen preparation, and thickness of the diffracting crystal. The observed intensity of fluorescent radiation from a number of common commercially pure metallic elements was compared under a constant primary radiation that can be closely maintained in practice. Intensities of fluorescent spectra were measured on constituents of Fe-Ni, Fe-Cr, and Fe-Ni-Cr alloys. Calibration curves correlating line intensity with weight percentage are included for binary Fe-Ni and Fe-Cr alloys. The thickness beyond which the fluorescent intensity becomes constant has been determined for pure iron, nickel, and chromium. Up to the above thickness for each element an empirical plot of fluorescent intensity against thickness of layer has been established. These empirical plots can be applied to measure the thickness of very thin coatings. Illustrations are given indicating the applications of the fluorescent analytical technique to the study of oxidation and diffusion processes in metallic systems. An aluminum holder is used for analyzing small quantities of powder derived from chemical or electrolytic extraction of certain phases from alloys. Fluorescent analysis on the extracted phase supplements the diffraction data when a wide solid solubility exists.