Scanning Electron Microscopy for Microstructural Analysis

Abstract

Probably the most exciting instrument which has been added to a metallographer’s repertoire of capabilities in the past several years has been the scanning electron microscope. Photographs taken with SEM’s have appeared widely in metallurgical literature and, in fact, it is not uncommon to see them in the daily newspapers or even in popular magazines. Perhaps the main reason for their wide use is that SEM images generally are easily recognizable; i.e., an SEM image of a small crystallite looks very much like one might expect a crystallite to look. At the same time, almost contrary to the above, the images are often so striking and show features in ways that no previous methods have been able to show, that the simple esthetics of the images cause them to appear in technical literature. Unfortunately, in many instances, these advantages of the instrument may have caused it to be used simply to produce a vast quantity of pretty pictures. In looking over the published technical literature of a few years ago, and even some of our own technical reports, it is obvious that SEM photographs were used in this way, and, quite frankly, frequently added nothing to the technical content of the publication. As might be expected, SEM photographs frequently adorned the covers of technical publications; in fact, the author counted a total of 14 covers containing such photos in a period of only 3 months on the relatively few technical publications that regularly pass across his desk. Now, however, this initial flurry of excitement appears to have quieted down, and SEM’s have acquired quite justified positions in many metallographic laboratories alongside metallographs, transmission electron microscopes, and other image- forming instruments Even though the SEM has had a tremendous impact on metallographic laboratories, it really hasn’t eliminated the need for those instruments which existed in metallographic laboratories prior to its introduction, but, rather, it serves to complement them.