The bulk diffusivity of 14C in monocrystals of the α phase was measured (table 2), at temperatures ranging from 596 to 1168K, by using radio-tracer and serial sectioning methods. At those temperatures where this work paralleled published Snoek-effect

determinations, good agreement was found between the directly and indirectly measured diffusion coefficients. It was deduced from this that the C atoms diffused interstitially only via octahedral sites in this phase. Overall, the results indicated a temperature dependence which was typical of the effect of a magnetic phase transition upon diffusion. The interstitial C diffusivity was more strongly affected by a stiffening of the lattice than was the vacancy-controlled self-diffusivity. Grain boundary diffusion of C in the α phase was observed at temperatures below 740K. On the basis of these and other results, it was concluded that C also diffused interstitially in the α-phase grain boundaries.

E.Budke, C.Herzig: Physica Status Solidi A, 1991, 127[1], 87-101

Table 2

Bulk Diffusivity of C in α-Fe