Structures of (112̄) Σ3 coincidence boundaries in titanium carbide

The high resolution TEM observation of 〈110〉 symmetric tilt grain boundaries in titanium carbide has shown that at a boundary near to the incoherent (112̄) Σ3 coincidence boundary there exists a periodic grain boundary structure consisting of two kinds of atomic arrangements. One is a mirror-symmetric atomic arrangement in the adjacent crystals to the boundary, and the other is a periodically mixed structure of mirror-symmetric and asymmetric arrangements. Two kinds of asymmetric structures are observed depending on a slight deviation from the ideal misorientation. This fact is explained by the DSC dislocation (b = a/6[112̄]) and lattice dislocation (b = a/2[011̄]) extended on their boundaries after dissociating into two partial dislocations, respectively. Further, the observed periodic structures of the boundary can well be explained by the DSC dislocations based on the CSL model and boundary dislocations predicted by the O-lattice model.