A Field Ion Observation of a Grain Boundary Node

In recent years there has been considerable interest in relating the structure of high angle grain boundaries to the properties of polycrystalline materials. It has been firmly established that these interfaces exhibit a highly complex, and often regular structure on the near atomic scale which can control the chemical or mechanical macro-behavior of the aggregate. However, unlike external surfaces, which can be probed by conventional surface spectroscopic and diffraction techniques, the internal structure of the grain boundary is usually only accessible with the transmission electron microscope. Interpretation of such images is at best complex and oftentimes the fine-scale structure is not observed due to resolution limitation of conventional imaging modes. The field ion microscope (FIM), on the other hand, offers both high resolution and a more direct imaging process. The FIM has been used in numerous grain boundary observations and more recently the results have been improved by computer reconstruction techniques providing detailed topographies of the interface. Presented in the present work is a computer reconstruction of the point of junction between three grains and two of the associated grain boundaries (see Figure 1).