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

The influence of proton irradiation on the diffusion of implanted Pd-103 or Au-195 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 mum (greater than or similar to 550 degreesC) or at some hundred nm (less than or similar to 550 degreesC). The results are in accordance with our previous suggestion that, in the absence of irradiation, in the high-diffusivity regime (greater than or similar to 10(-18) m(2) s(-1)) the diffusion is mediated by thermal vacancies, whereas at diffusivities below about 10(-18) m(2) s(-1) diffusion occurs by a direct interstitial mechanism which is unlocked by collective phason flips. (C) 2000 Elsevier Science B.V. All rights reserved.