Transmission electron microscopic observations of dislocations and faults, oriented in mirror planes of as-grown single grains of the icosahedral phase, showed that the Burgers vectors and associated fault vectors were perpendicular to the fault planes. The dislocations in as-grown samples were connected to more or less wavy faulted surfaces, which formed during their movement and usually lay close to mirror planes. It was noted that the displacement vector across one family of faults, and the Burgers vector of the associated moving dislocations, were the projection of a translation vector of the 6-dimensional lattice - onto the real space – which had a length of 0.480 or 0.297nm. The fault could be viewed as being a pure phason fault. The dislocations had a Burgers vector which was perpendicular to their plane of movement; that is, a 2-fold direction. They were therefore of pure edge-type, and exhibited the same residual contrast as that in periodic crystals when g||•b|| = 0. The geometry of the defects was consistent with dislocation motion that was controlled by a pure climb mechanism. The dislocations decreased their elastic energy by dissociation. The surface energy of the resultant fault was estimated to be 22mJ/m2. As this value was an upper bound on the phason-wall surface energy trailed by mobile dislocations, the corresponding dragging force was expected to be fairly low. The results suggested that climb processes had to be considered as realistic deformation modes at high temperatures in such materials.

Transmission Electron Microscopy Study of Dislocations and Extended Defects in As-Grown Icosahedral Al-Pd-Mn Single Grains. D.Caillard, G.Vanderschaeve, L.Bresson, D.Gratias: Philosophical Magazine A, 2000, 80[1], 237-53