Previous results which were relevant to the mechanisms that governed the mobility of dislocations in icosahedral quasi-crystals were summarized. These results arose from macroscopic deformation tests, conventional transmission electron microscopy, in situ straining experiments in a transmission electron microscope, and computer simulations. The experiments were best interpreted by assuming that dislocation motion was controlled by the thermally activated surmounting of Mackay-type clusters. An estimate was made here of the activation volume for this process. It was found that the activation volume for surmounting the clusters individually was an order of magnitude smaller than the experimentally observed one. The experimental observations could be interpreted in a consistent manner in terms of the Labusch-Schwarz theory of solution hardening in crystals. This considered the interpenetrating clusters to be so-called extended obstacles; a number of which were surmounted collectively.

Friction Mechanism of Dislocation Motion in Icosahedral Al-Pd-Mn Quasicrystals. U.Messerschmidt, M.Bartsch, M.Feuerbacher, B.Geyer, K.Urban: Philosophical Magazine A, 1999, 79[9], 2123-35