Grain-boundary self-diffusion in the B-kinetic regime was monitored by using the radiotracer method over temperature ranges which included the bulk order-disorder transition temperature. In the case of Fe diffusion in Fe3Al, the A2-B2 transition did not lead to any modification of the Arrhenius behavior, although a slight decrease in the triple-product values was observed below the B2-DO2 transition. In the case of FeCo, the A2-B2 transition caused a decrease in the pre-exponential factor of the triple product for both Fe and Co, while the diffusion activation energy was unaffected. The results were tentatively interpreted in terms of segregation effects and it was suggested that, due to segregation, the order-disorder transition temperature could be considerably different in grain boundaries, as compared to that in the bulk.

Grain Boundary Diffusion in B2 Intermetallic Compounds: Effect of Ordering on Diffusion in the Fe3Al and FeCo Compounds. Z.Tokei, J.Bernardini, D.L.Beke: Acta Materialia, 1999, 47[4], 1371-8