The Wagner’s equation is used to calculate the interdiffusion
coefficients based on the Al concentration profiles achieved by
the diffusion heat treatment of Fe2Al5 scale (Fig. 2). Fig. 3 shows
the interdiffusion coefficients calculated as a function of composition
from the experimentally measured concentration profiles for
980 C. The interdiffusion coefficients in the FeAl and a-Fe(Al)
phase strongly depends on Al content and shows a maximum at
about 28 at.% Al (transition concentration from the disordered