Self-diffusion mechanism in Ni-based L12 type intermetallic compounds

We propose a model for the self-diffusion in Ll(2) type A(3)B ordered compounds. In this structure, the atoms of the major element A can diffuse on their own sublattice (alpha sublattice) via the ordinary vacancy mechanism without disturbing the ordered arrangement. For the atoms of the minor element B, the same mechanism is possible for those distributed over the alpha sublattice as antisite atoms. If the number of the antisite atoms is not negligibly small, the long-range diffusion of B can be due largely to their migration over the alpha sublattice as impurity diffusion. The self-diffusion data in Ni3Al, Ni3Ga and Ni3Ge are discussed in the light of this model.