The structure of a <110> 90° grain boundary in Au was investigated using high-resolution transmission electron microscopy and atomistic simulation. It consisted of coherent segments, exhibiting the extended 9R configuration described by Medlin et al., with superimposed line defects to accommodate the coherency strain. Two types of defects were observed, crystal dislocations and disconnections, where the latter exhibited step nature in addition to dislocation character. Both types of defect were identified by high-resolution transmission electron microscopy in combination with circuit mapping, and their parameters were shown to be consistent with the topological theory of interfacial defects. Moreover, the misfit-relieving function of observed defect arrays, their influence on interface orientation and the relative rotation of the adjacent crystals was elucidated. During observation, defect decomposition was observed in a manner which conserved Burgers vector and step height. One of the decomposition products was glissile, consistent with the 'glide/climb' rules for interfacial defects. This glissile motion was also found by atomistic simulation of the disconnection when an applied strain was imposed. The γ-surface for the interface was calculated and showed that no alternative boundary structure was stable, confirming, consistent with experimental observation, that defects separating different configurations were not feasible.

A Study of the Accommodation of Coherency Strain by Interfacial Defects at a Grain Boundary in Gold. R.C.Pond, D.L.Medlin, A.Serra: Philosophical Magazine, 2006, 86[29-31], 4667-84