The migration of Si in the ' phase of an intermetallic compound with the L12 structure was studied at 1173 to 1598K by using diffusion couples of Ni-24.2Al versus Ni-22.3Al-3.14mol%Si. Diffusion profiles in the annealed diffusion couples were measured by means of electron probe micro-analysis. The diffusion coefficients of Si in the ' phase of 24.2mol%Al material were

deduced from the diffusion profiles by using Hall's method. It was found that the temperature dependence of the diffusion coefficient could be described by:

D(m2/s) = 0.48 exp[-390(kJ/mol)/RT]

The activation energies were found to be closely related to the substitution behavior of Si atoms in the L12 lattice sites of '.

Y.Minamino, T.Yamane, S.Saji, K.Hirao, S.B.Jung, T.Kohira: Journal of the Japan Institute of Metals, 1994, 58[4], 397-403