Measurements were made of the diffusivity of B in nanocrystalline Fe. It was shown that the B diffused slower in the grain boundaries than in the lattice. The diffusion data were analyzed in terms of a new type of diffusion kinetics; referred to as type-C'. In these kinetics, the diffuser was confined to the grain boundaries by a large segregation factor. Therefore, even though the lattice diffusion was faster than grain-boundary diffusion, the grain-boundary diffusion coefficient was easily obtained. Overall, the present data (table 49) could be described by:

D (m2/s) = 1.7 x 10-11exp[-0.59(eV)/kT]

H.J.Höfler, R.S.Averback, H.Gleiter: Philosophical Magazine Letters, 1993, 68[2], 99-105

Table 49

Effective Diffusivity of B in Nanocrystalline Fe