Samples which had been plastically deformed, using high stresses at temperatures ranging from 20 to 800C, were studied by means of transmission electron microscopy. The activation of 1/3<11•0>(00•1) basal slip, as well as the first type of 1/3<11•0>{1¯1•0} prismatic slip, was observed. Dislocation configurations in the basal plane revealed the role that was played by Peierls forces acting along the screw orientation. It was easier for a dislocation to cross-slip in the prismatic plane than to lie, in the basal plane, along an orientation other than the screw direction. In the basal plane, as well as in the prismatic plane, no dislocation dissociation could be resolved under weak-beam imaging conditions. The occurrence of cross-slip was favoured by numerous pinning points on screw dislocations; thus giving rise to dipole dragging. At temperatures ranging from 20 to 500C, deformation proceeded via dislocation glide in the basal and prismatic planes; with frequent cross-slip between these planes. At 800C, a change in the mobility of edge dislocations on the prismatic plane was detected and was attributed to lattice friction acting in the (00•1) orientation or to dislocation dissociation out of the glide plane.

M.Audurier, J.L.Demenet, J.Rabier: Philosophical Magazine A, 1998, 77[4], 825-42