Anisotropic diffusion behaviour of Co-60 in decagonal Al-Ni-Co single quasicrystals

摘要

The orientation dependence of Co-60 self-diffusion has been investigated in stable decagonal single quasicrystals of Al72.2Ni11.8Co16.0 by means of the radiotracer method. Over a wide range from 803 to 1210 K the temperature dependence of the Co diffusivities along the periodic (tenfold- axis) and the aperiodic (twofold- axis) directions can be described each by a single set of Arrhenius parameters. The temperature dependence of the diffusion coefficients yields the Arrhenius parameters D-0(per) = 1.54 x 10(-1) m(2) s(-1), Q(per) = 277.4 kJ mol(-1), D-0(aper) = 3.96 x 10(-1) m(2) s(-1) and Q(aper) = 289.0 kJ mol(-1), respectively. The mobility of Co is slightly faster along the periodic direction. This anisotropic effect is discussed in the content of results of analogous diffusion investigation in icosahedral quasicrystals from our laboratory and with literature data on quasicrystals. It is concluded that Co diffusion in decagonal Al-Ni-Co quasicrystals in the periodic as well as in the aperiodic direction in the entire temperature range very probably occurs via a vacancy mechanism. [References: 27]