Dislocation mobility versus dislocation substructure controlled deformation of icosahedral Al–Pd–Mn single quasicrystals

This paper compares new high-voltage electron microgaphs of the dislocation structure of icosahedral Al–Pd–Mn specimens deformed at a high temperature (≅800°C) with those deformed at a low temperature (610°C). At all temperatures, the dislocations consist of almost straight segments on different planes. However, planar faults trailed by the dislocations have been observed at low temperatures only. The temperature dependence of the steady-state flow stress is modelled based on an evolution law of the dislocation density proposed before including recovery, and by considering the contribution of long-range dislocation interactions to the flow stress. Owing to the thermally activated recovery of the microstructure, the activation energy of deformation measured experimentally turns out to be higher than the energy of the dislocation mobility, explaining the unreasonably high experimental values.