Diffusion ofMn54andFe59in icosahedral Al-Pd-Mn single quasicrystals

Self-diffusion of ${}_{}{}^{54}{}_{}{}^{}\mathrm{Mn}$ and diffusion of ${}_{}{}^{59}{}_{}{}^{}\mathrm{Fe}$ was studied in icosahedral single quasicrystals of ${\mathrm{Al}}_{70.4}$ ${\mathrm{Pd}}_{21.2}$ ${\mathrm{Mn}}_{8.4}$. The radiotracer method in combination with serial sectioning of the diffusion samples was used to determine concentration depth profiles. The temperature dependences of diffusion are expressed by Arrhenius equations with the following activation enthalpies ($Q$) and pre-exponential factors ($D_0$): Mn: $Q=1.99\mathrm{}$ eV; $D_0=8.91\mathrm{}\times {10}^{-4\mathrm{}}$ ${\mathrm{m}}^2$ ${\mathrm{s}}^{-1\mathrm{}}$, Fe: $Q=2.61\mathrm{}$ eV; $D_0=1.63\mathrm{}\times {10}^{-2\mathrm{}}$ ${\mathrm{m}}^2$ ${\mathrm{s}}^{-1\mathrm{}}$. The results are compared with the scarce literature data on quasicrystals and with data on diffusion in fcc aluminium and in iron aluminide. The quasicrystal data are not significantly different from those in related crystalline materials, for which a vacancy-mediated mechanism is generally accepted for diffusion. Deviation from an Arrhenius behavior as predicted for phason-assisted diffusion could not be detected.