An Atomistic Study of Interfacial Diffusion in Lamellar TiAl Alloys

In this paper we investigate self-diffusion of Ti and Al along interfaces present in the lamellar L1₀ TiAl by atomistic computer modeling. The interactions between the atoms are described by central-force many-body potentials. The approach adopted is similar to that used in earlier atomistic modeling of bulk diffusion in TiAl [1, 2]. Both the formation and migration of vacancies is examined. The interfaces studied are the three types of –interfaces: ordinary twin, pseudotwin and 120° rotational fault. For the latter two interfaces the diffusion was investigated not only for the stoichiometric case but also when the interfaces possess a surplus of titanium in the form of a layer with the composition and structure of Ti₃Al, as was found in an earlier Monte Carlo study of titanium segregation to these interfaces. The calculations suggest that the diffusivity along –interfaces is higher than in the bulk. However, the difference between bulk and interfacial diffusivity is not as drastic as it may be encountered in grain boundaries. At the same time the above mentioned surplus of Ti appears to affect the interfacial diffusion only marginally.