Molecular dynamics simulations of nanometric metallic multilayers: Reactivity of the Ni-Al system

The reactivity of a layered Ni-Al-Ni system is studied by means of molecular dynamics simulations, using an embedded-atom method type potential. The system, made of an fcc-Al layer embedded in fcc-Ni, is initially thermalized at the fixed temperature of 600 K. The early interdiffusion of Ni and Al at interfaces is followed by the massive diffusion of Ni in the Al layer and by the spontaneous phase formation of B2-NiAl. The solid-state reaction is associated with a rapid system heating, which further enhances the diffusion processes. For longer times, the system may partly lose some its B2-NiAl microstructure in favor of the formation of L1(2)-Ni(3)Al. This stage is controlled by the diffusion of Al in the Ni-rich phase, and a layer-by-layer development of the new phase is observed.