New high-voltage electron micrographs of the dislocation structure of icosahedral specimens deformed at high temperatures (800C) were compared with those deformed at low temperatures (610C). At all temperatures, the dislocations consisted of almost straight segments on different planes. However, planar faults trailed by the dislocations were observed at low temperatures only. The temperature dependence of the steady-state flow stress was modelled on the basis of an evolution law of the dislocation density, before including recovery, and by considering the contribution of long-range dislocation interactions to the flow stress. Due to thermally activated recovery of the microstructure, the activation energy for deformation as measured experimentally was higher than the energy for dislocation mobility; thus explaining the unreasonably high experimental values.

Dislocation Mobility Versus Dislocation Substructure-Controlled Deformation of Icosahedral Al–Pd–Mn Single Quasicrystals. U.Messerschmidt, B.V.Petukhov, M.Bartsch, C.Dietzsch, B.Geyer, D.Häussler, L.Ledig, M.Feuerbacher, P.Schall, K.Urban: Materials Science and Engineering A, 2001, 319-321, 107-10