On misfit-compensating ledges/disconnections

Abstract The evidence for and use of the term misfit-compensating ledge or disconnection as a description for a type of defect found at some interphase boundaries is reviewed and further developed. Analyses are presented for the fcc/hcp, trigonal/hcp and bcc/hcp boundary cases and a new computer near coincidence site (NCS) simulation of the bcc/hcp case is undertaken. The results of the NCS analysis are in good agreement with previous O-lattice modeling. These results are also equivalent to those obtained by direct inspection of the dichromatic complex of the structures forming the interface. The analyses were compared with TEM observations of interphase boundaries formed in a Ti–6.62%Cr alloy where the disconnections were observed to be arranged in pairs and to have Burgers vectors with a component of 1/2[0001]. The observations are interpreted in terms of the dichromatic complex.