The tracer self-diffusion coefficients of 51Cr in high-purity Fe-50wt%Cr alloy were determined, at 923 to 1273K (figure 18), by using the sputter micro-sectioning technique. A linear Arrhenius plot, across the α-σ phase transformation at 1103K, was observed. This was consistent with the suppression of σ-phase formation by purification. The results (table 58) could be described by:

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

This activation energy for the self-diffusion of Cr was much lower than the 293kJ/mol which had been reported for 1223 to 1523K.

M.Sugihara, Y.Yamazaki, S.Takaki, K.Abiko, Y.Iijima: Materials Transactions, 2000, 41[1], 87-90

Table 59

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