Abstract: The atomic level structures of fcc/bcc interfaces in an Fe-9Ni alloy have been examined by means of HREM. It has been found that the orientation of γ /α interface had great effects on its atomic structure. These interfaces with different orientations may be composed of only structural ledges, structural ledges with misfit dislocations,superledges with misfit dislocations or only misfit dislocations. A structural model of growth ledge was suggested. The terrace of growth ledge was composed of structuralledges or misfit dislocations. The atomic structure of the riser of growth ledge was the same as that of the side facet of γlath, which is composed of saperiedges with misfitdislocations.

Key words: Fe-9Ni alloy, austenite, martensite, interface structure, electron microscopy