COMPARISON OF FEG-STEM AND AES MEASUREMENTS OF EQUILIBRIUM SEGREGATION OF PHOSPHORUS IN 9-PERCENT CR FERRITIC STEELS

The equilibrium grain boundary segregation in a series of 9% Cr ferrit ic steel alloys, doped with different concentrations of P impurity, ha s been measured by analytical scanning transmission electron microscop y (STEM) and Auger electron spectroscopy (AES). Both P and Cr segregat ion to boundaries was detected using both methods. Different levels of sophistication have been used to process the spectral data in order t o derive the equivalent fractional monolayer concentrations of the seg regants. The distributions of measurements from individual grain bound aries are displayed as histograms, and the different analytical proces ses are contrasted by comparing the means and standard deviations of t hese distributions. The STEM and AES results for P are in agreement ir respective of the technique and analytical procedure used, However, a systematic divergence occurs in the Cr results, which is considered to arise from contributions from Cr-rich boundary precipitates to the AE S spectra that cannot be accurately separated. (C) 1997 by John Wiley & Sons, Ltd.