Self-diffusion of Ni and Co in decagonal Al-Ni-Co quasicrystals

Single-quasicrystals of decagonal Al72.6Ni10.5Co16.9 (D-AlNiCo) were produced by the flux-growth technique. Diffusion of Co-57 and Ni-63 was studied by the radiotracer serial sectioning method in both principal directions of the decagonal quasicrystals. In addition Ni-63 diffusion was studied in coarse-grained polycrystals of D-Al70.2Ni15.1Co14.7 grown by the Bridgman technique. Close similarities between the diffusion behaviour in pure Co, Ni and in D-AlNiCo, and in particular the small diffusion anisotropy suggest a vacancy-mediated diffusion mechanism for D-AlNiCo. Similar magnitudes of the Ni diffusivities in D-Al72.6Ni10.5Co16.9 and in D-Al70.2Ni15.1Co14.7 show that. the composition dependence of diffusion within the phase field of the decagonal quasicrystalline phase is weak. The results are discussed together with recent literature data for diffusion in D-AlNiCo, with diffusion ill uniaxial metals anti in icosahedral Al-Pd-Mn quasicrystals (I-AlPdMn).