A dislocation-based description of grain boundary dissociation: Application to a 90 degrees < 110 > tilt boundary in gold

High resolution transmission electron microscopy (HRTEM) observations and a tomistic simulations of {1 (1) over bar1}/{121} facets in a gold 90 degrees tilt boundary show the presence of a similar to 10 Angstrom wide layer wit h stacking faults distributed one to every three close-packed planes. This interfacial reconstruction, which forms the rhombohedral 9R stacking arrang ement, is similar to that found previously for near-Sigma = 3{112} boundari es in low stacking fault energy metals. We discuss a general approach for p artitioning grain boundary orientation into a set of Shockley partial dislo cations and then apply this description to the {11}/{121} interface. The an alysis explains both the distribution of faults and the geometry of the loc al plane bending and shows, further, that the 9R stacking occurs in both th e Sigma = 3{112} and {1 (1) over bar1}/{121} interfaces due to the similar ratios of 30 degrees and 90 degrees Shockleys in both cases. Finally, we di scuss limitations of this description, in particular concerning a 1/8[(1) o ver bar 01] relaxation that is predicted by the atomistic simulations. publ ished by Elsevier Science Ltd on behalf of Acto Materialia Inc.