Atomistic simulations of diffusion mechanisms in off-stoichiometric Al-rich Ni3Al

This paper presents dynamics simulation results of diffusion in off-stoichiometric Al-rich Ni3Al (Ni73Al27) at temperature ranging from 1300 to 1550 K. The interatomic forces are described by the Finnis-Sinclair type N-body potentials. Particular attention is devoted to the effect of the extra 2% of Al atoms sitting on the Ni sublattice as antisite point defects (AlNi) on diffusion. Simulation results show that Ni atoms mainly diffuse through the Ni sublattice at the temperatures investigated. Al atoms diffuse via both the intrasublattice and antistructure bridge (ASB) mechanisms. The contribution to Al diffusion from the ASB mechanism decreases at the lower temperature (T<1400 K). The presence of antisite point defects (AlNi) enhances both Al and Ni diffusion in Ni73Al27. The Ni-Al coupled diffusion effect is observed and understood at the atomic level for the first time