An experimental study was made of Ni diffusion, in single-grained samples of an icosahedral quasicrystalline compound, at 699 to 1074K. A radiotracer technique, together with serial sectioning, was used to determine the concentration versus depth profiles. No deviation from Arrhenius behaviour was detected over the present temperature range, and the results (table 3, figure 2) could be described by:

D (m2/s) = 5.3 x 10-3 exp[-209(kJ/mol)/RT]

The most interesting observation was that Ni diffusion, and the diffusion of other transition-metal elements, was much slower than the diffusion of elements such as Ge and Zn. The activation enthalpies for the diffusion of transition-metal elements were also considerably greater than those found for non-transition metal elements. It was concluded that the diffusion of Ni atoms was most likely to proceed via a vacancy mechanism over Al and Pd sites.

Solute Diffusion of Ni in Icosahedral Al-Pd-Mn Quasicrystals. T.Zumkley, H.Nakajima, T.A.Lograsso: Philosophical Magazine A, 2000, 80[5], 1065-74

Figure 2

Diffusivity of 63Ni in Al70Pd21Mn9

Table 3

Diffusivity of 63Ni in Al70Pd21Mn9