The Electron "licroprobe X-!{ay Analyscr conceivcd b ' R C.\S'L\I: \G and A. Cl'!: '\ lEI( in 1949 has been developcd as an extremelv po\\'crful tool in spcctrochcmical analysis for a wide range of applications, ranging from qualitative elcmcntary distribution studies, to highly localiscd quantitatin analysis on a one micron scale. \\'ith the increasing number oi' versatile instruments, commcrcially available, the domain of applications - in metallurgy, solid state physics, mineralogy and geology, biology and medicine, arts and archeology - is rapidly expanding, particularly because reliable quantitative analyses can be achieved. It is well established that in multicomponent specimens, the relative x-ray intensity generated by the electron bombardment - i.e. the intensity ratio of the characteristic x-ray radiation emitted under identical experimental conditions by the specimen and a calibration standard - is not directly correlated to the elementary mass concentration. The use of a wide scale of carefully prepared homogeneous calibration standards is generally very tedious and restricted to binar)' systems. For more complex specimens, the conversion of recorded x-ra)' intensity ratios to elementary mass concentration requires, besides carefule selection of experimental conditions, an adequate correction calculation to take account oi' the various physical phenomenas occurring in the tarp;et - electron retardation, electron backseattering, x-ray excitation efficieney, fluorescence enhaneement by eharaeteristic and continuous radiation and x-ray mass absorption.

The electron probe microanalyzer, a versatile tool for the analysis of areas as small as one micron in diameter, has been used at Goddard Space Flight Center in applications ranging from materials research to analysis of failures in mechanical parts. Methods of using the probe and representative results obtained are illustrated by several examples that include bonding of thermoelectric materials, alloy development, and analysis of materials failure.

Continuously cast steel often exhibits a nonhomogeneous composition resulting from elemental segregation during solidification. Concentrated regions of phosphorus, carbon, sulfur, manganese and other elements can have detrimental effects on properties. At present, measurement of segregation is by subjective assessment of sulfur prints or chemical analysis of drillings. Detailed elemental distribution measurements require expensive and time consuming measurements using x-ray mapping facilities. This paper outlines a newly developed technique in which segregation patterns are determined by applying an etchant to produce selective darkening of phosphorus rich regions. A CCD video camera and computer are used to assess the etched sample and construct an approximate phosphorus distribution map. X-ray maps of phosphorus produced by a computer controlled electron microprobe are used to check the accuracy of the technique. Further processing techniques are applied to x-ray and etch maps to obtain measures of segregation.