The tracer self-diffusion coefficients of 51Cr and 59Fe in high-purity Fe-50wt%Cr alloy were determined, at 923 to 1273K (figure 16), by using the sputter micro-sectioning technique. A linear Arrhenius plot, across the α-σ phase transformation at 1103K, was observed for each diffusant. This was consistent with the suppression of σ-phase formation by purification. The results (tables 18 and 19) could be described by:

Cr:     D (m2/s) = 5.4 x 10-5 exp[-251(kJ/mol)/RT]

and

Fe:     D (m2/s) = 3.0 x 10-5 exp[-243(kJ/mol)/RT]

These activation energies for the self-diffusion of Cr and Fe were much lower than the 293 and 312kJ/mol, respectively, which had been reported for temperatures ranging from 1223 to 1523K.

Self-Diffusion in High-Purity Fe-50mass%Cr Alloy. M.Sugihara, Y.Yamazaki, S.Takaki, K.Abiko, Y.Iijima: Materials Transactions, 2000, 41[1], 87-90

Table 18

Self-Diffusion of 51Cr in Fe-50wt%Cr

Table 19

Self-Diffusion of 59Fe in Fe-50wt%Cr

Figure 16

Diffusivity of 51Cr and 59Fe in Fe-50wt%Cr