The migration of Cu, Fe, and 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-24.1Al-4.73Cu, Ni-24.2Al versus Ni-23.7Al-3.52Fe, and 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 Cu, Fe, and 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 dependences of the diffusion coefficients could be described by:

Cu:     D(m2/s) = 5.5 x 10-3exp[-323(kJ/mol)/RT]

Fe:     D(m2/s) = 2.7 x 10-2exp[-347(kJ/mol)/RT]

Si:     D(m2/s) = 4.8 x 10-1exp[-390(kJ/mol)/RT]

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

Diffusion of Cu, Fe and Si in L12-Type Intermetallic Compound Ni3Al. Minamino, Y., Yamane, T., Saji, S., Hirao, K., Jung, S.B., Kohira, T.: Journal of the Japan Institute of Metals, 1994, 58[4], 397-403

Table 12

Arrhenius parameters for 59Fe grain-boundary diffusion in Ni3Al Alloys