Abstract
In part I, we have shown experimentally that the large amount of work softening is due to decreasing activation enthalpy for plastic deformation with increasing plastic strain. Based on the Peierls mechanism of the dislocation glide, the plastic deformation process in a quasiperiodic lattice is modelled. In the model, we assume high and low activation enthalpies, corresponding to large and small Peierls potentials, of the kink pair formation in the quasiperiodic Peierls potential. In an unstrained high-quality quasicrystal, the dislocation glide is essentially controlled by the high activation enthalpy whereas, in a highly strained state where a high density of phason defects is introduced, the dislocation glide is controlled by the low activation enthalpy; parts with a large Peierls potential can be overcome by the side motion of kinks produced at parts with a small Peierls potential.