The bulk diffusion of Sn in the α and γ phases of alloys containing between 0.3 and 1.6wt%Sn was studied. The concentration gradients were determined by using electron probe analyses, and the interdiffusion coefficients were calculated by using the Grube-Jedele method. At concentrations of up to 1.6wt%Sn, the diffusivity was found to be independent of the concentration. The activation energies for bulk Sn diffusion were also determined. Lower values were found for the α-phase. The results (table 200) could be described by:

α-Fe:     D (m2/s) = 8.00 x 103 exp[-38.2(kcal/mol)/RT]

γ-Fe:     D (m2/s) = 2.32 x 10-4 exp[-44.3(kcal/mol)/RT]

The interdiffusion coefficients decreased when Cu was present.

N.Sarafianos: Materials Science and Engineering, 1986, 80[1], 87-91

Table 199

Diffusivity of 71Ge in Fe73.5Si13.5B9Nb3Cu Nanocrystals