Interface morphology of nanosized Si embedded in Al matrix

Al/ Si interface morphologies of rapid quenched Al - Si alloys are observed by high resolution transmission electron microscopy. Si nanocrystals embedded in Al matrix are in particle and rod shapes. The Al/ Si interface of particles is mainly amorphous while that of rods is essentially semicoherent with a cube - cube relationship. From thermodynamic and mechanic points of view, the interface morphologies are related to the size of the nanocrystals. It is found that the semicoherent interface of nanocrystals can exist even if the interface strain reaches one- fourth as long as the size of the nanocrystals is small enough. In addition, the semicoherent interface is stable against growth when the nanocrystals' sizes are smaller than a critical size. This is because this growth does not lead to drop of the unit internal energy of the nanocrystals.