Using transmission electron microscopy and in situ atomic force microscopy, the activation of dislocation sources in γ-phases of Ni-base superalloys was investigated. Sources, at the origin of slip bands containing numerous pile-ups of several tens of dislocations, were heterogeneously distributed. They were a few micrometers apart. The physical reason for such an heterogeneity was the presence of short-range order which induced a high friction stress acting against the dislocation movement. A description of the solid solution as a combination of soft and hard areas was proposed. dislocation sources could be activated in areas where the friction was low while the presence of hard zones hinders their operation. This distribution of hard and soft zones results from the local variations of short-range order. The distribution of the sources indicates that soft regions were a few micrometers apart.

Activation of Dislocation Sources in γ-Phases of Nickel-Base Superalloys Studied by use of Atomic-Force Microscopy and Transmission Electron Microscopy. F.Pettinari-Sturmel, C.Coupeau, N.Clément, A.Coujou: Materials Science and Engineering A, 2004, 387-389, 103-8