The evidence for and use of the term misfit-compensating ledge or disconnec
tion as a description for a type of defect found at some interphase boundar
ies is reviewed and further developed, Analyses are presented for the fcc/h
cp, trigonal/hcp and bcc/hep boundary cases and a new computer near coincid
ence site (NCS) simulation of the bcc/hep case is under-taken. 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 o
f the dichromatic complex of the structures forming the interface. The anal
yses were compared with TEM observations of interphase boundaries formed in
a Ti-6.62%Cr alloy where the disconnections were observed to be arranged i
n pairs and to have Burgers vectors with a component of 1/2[0001], The obse
rvations are interpreted in terms of the dichromatic complex. (C) 2001 Acta
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