WEAK-BEAM TRANSMISSION ELECTRON-MICROSCOPY IMAGING OF SUPERDISLOCATIONS IN ORDERED NI3AL

In order to provide quantitative information about dissociation modes of superdislocations in ordered Ni3Al, weak-beam transmission electron microscopy observations of dislocation core structures have been comb ined with image simulations. The use of image simulations allowed us t o interpret intensity peaks on weak-beam micrographs in terms of actua l partial dislocations and splitting distances, and corresponding faul t plane energies could be subsequently inferred. A description of the main parameters to be considered in the calculations is given below an d the validity of such calculations is discussed in a critical way. Th e impact of these results on interpretation of the anomalous flow stre ss behaviour in Ni3Al is also addressed.