Atomistic simulations of diffusion in off-stoichiometric Ni-rich Ni3Al (Ni77Al23) at 1300 to 1550K and a comprehensive analysis of the composition-dependence of Ni and Al diffusion in γ’-Ni3Al with 3 compositions (73, 75 and 77at%Ni) were presented. The interatomic forces were described by Finnis–Sinclair type N-body potentials. The simulations revealed that Ni diffusion was dominated by Ni vacancy mechanisms. The Al diffusion occurred via both intra-sublattice and anti-structure bridge mechanisms in Ni77Al23 at the temperatures investigated. The presence of an extra 2% of antisite defects enhanced the diffusion of both Ni and Al, in off-stoichiometric Ni-enriched Ni3Al, via the vacancy–antisite interaction. The single-vacancy diffusivity of Ni and Al in Ni3Al of 3 compositions (73, 75, 77at%Ni) at the above temperatures were corrected with the thermal equilibrium concentration of point defects. The corrected Ni and Al diffusion data were in good agreement with available experimental data. The Ni diffusivity decreased with Ni concentration, while the Al diffusivity exhibited a minimum at the stoichiometric composition in the simulated temperature range.

Computer Modeling of Diffusion in Ni-Rich Ni3Al and Composition Dependence of Diffusion in γ’ Ni3Al. Duan, J.: Journal of Physics - Condensed Matter, 2008, 20[19], 195221