Lavrova G. Kinetics of phason defects and radiation damage in quasicrystals

A theoretical method of finding dislocation mobility in quasicrystals is proposed in the thesis using basic relations of thermodynamics and hydrodynamics and taking into account peculiarities of quasicrystal structure, the presence of vacancies and phasons. The expressions for dislocation mobility in an icosahedral quasicrystal are found taking into account the redistribution of vacancy concentration and inelastic transformations related to phason deformations. Direct expressions for the contributions of elastic deformations, viscous flow, phason defects, and the interaction of elastic fields with vacancy-induced dilatation are found using the self-similar solution of equations of dislocation displacement field dynamics in a quasicrystal. Based on the known mechanisms of radiation swelling of crystals, models of this phenomenon in quasicrystals are described. A system of rate equations for intrinsic point and phason defects is formulated. It is shown that the swelling rate of quasicrystals is lower than the swelling rate of crystals. The capture efficiency of point defects by a dislocation loop with a complementary ring of phason defects is found by numerical methods. It is shown that phasons notably reduce the dislocation bias to interstitial atoms, hence quasicrystalline materials are expected to have an increased resistance to vacancy swelling. Phason defects are considered in the model of non-coincident sites in the shear layer of a non-periodic structure. It is shown that phasons significantly reduce the dislocation bias to interstitial atoms. Therefore, quasicrystalline materials are expected to exhibit increased resistance to vacancy swelling.