ON THE RELATIONSHIP BETWEEN UNUSUAL MECHANICAL-PROPERTIES AND DEFORMATION SUBSTRUCTURES IN ORDERED NI3AL

Ni3(Al,1%Ta) single crystals have been deformed in compression in the temperature range of the flow stress anomaly (300-770 K). The strain r ate sensitivity of the flow stress has been examined by the stress rel axation technique. The core structures of the superdislocations on (11 1) and (001) planes have been observed using weak beam transmission el ectron microscopy (TEM). The TEM observations and the strain rate sens itivity tests both define two temperature regimes over the investigate d temperature range. The importance of using weak beam image simulatio ns to derive actual antiphase boundary energies from the experimental observations has been emphasized.