Contrast from large prismatic dislocation loops

Abstract

Abstract Geometrical analysis of prismatic dislocation loops enables their diffraction contrast to be predicted and the Burgers vector to be determined without necessitating g.b=0 tilting experiments. For large loops, inspection of the image also enables the habit plane to be determined for most cases. The results are based on analyses of perfect loops on {111} in f.c.c. metals which show double-arc contrast, but the predictions can be applied to any crystal system. Double-arc contrast disappears as the loop rotates towards pure edge orientation. The usefulness of strain contrast imaging of large loops is also discussed.