Heterogeneous nucleation of precipitates in Co5Sm crystals

A transmission electron microscopic investigation has been undertaken of the heterogeneous nucleation of precipitates present in Co5Sm crystals. By means of computer simulation of the displacement fringe contrast, planar extrinsic faults lying in the basal plane and bordered by Frank partial dislocations were identified as Co17Sm2 precipitates which nucleate at prismatic c-edge dislocations. Further nucleation centres, which were also found, are a-edge dislocation dipoles in the basal plane, prismatic a-edge dislocations and c + a screw dislocations. These experimental results are in agreement with calculations according to continuum theory. (author)