On some practical aspects of orientation determination using electron channeling patterns

A brief survey was made of the methods currently used for indexing of electron channeling patterns. Special attention was given to orientation determination of individual grains in a polycrystalline sample, for trace analysis and for determination of the relative orientation of the grains. The accuracy of various procedures was tested on alpha brass samples containing annealing twins. It was found that the beam direction (z) can be routinely determined with an error of less than 0.1° and the “in‐plane” directions (x, y) with an error of less than 1°. This accuracy is sufficient to determine the slip planes in a unique manner using their slip traces on the surface. It is also sufficient to determine relative orientations of the grains with average errors of less than 0.5° in rotation angle and in the position of the rotation axis. It was shown that this accuracy seems to be sufficient for distinguishing most special, nearcoincidence grain boundaries in polycrystalline samples. Procedures used for crystallographic description of a polycrystalline specimen are discussed. These include: indexing of the channeling patterns, orientation determination of the grains, trace analysis, and misorientation (relative orientation) determination. Accuracy of these procedures is estimated through the study of twin‐oriented grains in alpha brass. Possibilities of improving the accuracy and speeding up the analytical procedures by using appropriate microcomputer programs are indicated.