Diffusion of 103Pd and 195Au in icosahedral Al70.2Pd21.3Mn8.5 under proton irradiation

The influence of proton irradiation on the diffusion of implanted 103Pd or 195Au atoms in icosahedral Al70.2Pd21.3Mn8.5 has been investigated by means of a radiotracer technique. After implantation, the specimens were diffusion-annealed under simultaneous 0.5 or 1 MeV proton irradiation. The serial sectioning of the specimens was done either by precision grinding or Ar+-beam sputtering depending on whether the mean diffusion depths lay in the regime 10–100 μm (≳550°C) or at some hundred nm (≲550°C). The results are in accordance with our previous suggestion that, in the absence of irradiation, in the high-diffusivity regime (≳10−18 m2 s−1) the diffusion is mediated by thermal vacancies, whereas at diffusivities below about 10−18 m2 s−1 diffusion occurs by a direct interstitial mechanism which is unlocked by collective phason flips.