The effect of phason defects on the radiation-induced swelling of quasicrystalline materials

The radiation-induced vacancy swelling of quasicrystals is considered. In quasicrystals, the dislocation kinetics involves the formation of phasons: vacancy- and interstitial-like localized topological defects. Phasons interact with radiation-induced point defects (PD; vacancies and interstitials) and influence the swelling behavior of quasicrystals. After absorption of vacancies, phasons of the interstitial type transform into phasons of the vacancy type and vice versa. In other words, phasons are the recombination centers of alternating polarity for PD. Assuming that (i) the production rate of phasons is proportional to the dislocation climbing rate and (ii) voids are the sinks for mobile phasons, the set of rate equations for PD and phasons is formulated and analyzed both analytically and numerically. It is shown that the swelling rate is lower in quasicrystals compared with crystals. Growth rates of loops and voids, as well as the swelling rate, strongly depend on the phason concentration which is controlled by phason diffusion to sinks.