Self- Diffusion of Ni and Co in Decagonal AI-Ni-Co Quasicrystals

摘要

Single-quasicrystals of decagonal Al_(72.6)Ni_(10.5)Co_(16.9) (D-AlNiCo) were produced by the flux-growth technique. Diffusion of ~(57)Co and ~(63)Ni was studied by the radiotracer serial sectioning method in both principal directions of the decagonal quasicrystals. In addition ~(63)Ni diffusion was studied in coarse-grained polycrystals of D-Al_(70.2)Ni_(15.1)Co_(14.7) grown by the Bridg-man 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-Al_(72.6)Ni_(10.5)Co_(16.9) and in D-Al_(70.2)Ni_(15.1)Co_(14.7) 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 in uniaxial metals and in icosahedral Al-Pd-Mn quasicrystals (I-AlPdMn).