Serration and dissociation of edge dislocations in low angle tilt boundaries in gold

Abstract

The fine structure of a variety of low angle tilt boundaries in gold has been studied by high resolution transmission electron microscopy and electron diffraction in thin-film bicrystal specimens. The boundaries were found to consist of arrays of dislocations running on average along the tilt axis as expected. However, in the general case where the tilt axis did not lie in a {111} plane the dislocations were serrated into a “hill and valley” structure which allowed them to dissociate on {111} planes into partial dislocations and patches of stacking faults. This configuration produced a decrease in core energy at the expense of increased line length energy and is expected to be a general feature of dislocations in low angle tilt boundaries in metals with low (and moderately low) stacking fault energies. The importance of this phenomenon in the interpretation of measurements of pipe diffusion along dislocations in low angle tilt boundaries is discussed.