Plastic deformation of icosahedral Al-Pd-Mn single quasicrystals - II. Interpretation of the experimental results

Experimental data on the plastic deformation of icosahedral Al-Pd-Mn single quasicrystals are discussed in terms of dislocation models. The occurrence of a yield drop followed by a range of steady state deformation is explain ed by the effects of dislocation multiplication and recovery on both the mo bile dislocation density and the internal stress. The influence of transien t phenomena during the measuring procedures of the activation parameters is estimated. The activation volume of deformation is a unique function of th e stress. The activation enthalpy and the Gibbs free energy, calculated by Schoeck's formula, assume approximately constant values above 700 degrees C but decrease strongly below this temperature. In the temperature range whe re steady state deformation is possible, probably the flow stress is contro lled by both the friction mechanism of moving dislocations and the recovery processes taking place during deformation.