Phase formation of NiAl3 on lateral diffusion couples

The kinetics of NiAl3 phase growth is studied on lateral diffusion couples in the temperature range from 375 to 450 °C. The lateral diffusion couple consists of an Al-rich source on a Ni2 Al3 thin film. Analytical electron microscopy is used to determine the crystal structures and chemical compositions of the growing phases. The results show that: (1) Al is the dominant moving species in the growing NiAl3 phase; (2) an equilibrium concentration of Al is established during the growth; and (3) the growth has a parabolic dependence on the annealing time. The study of NiAl3 growth kinetics on lateral diffusion couples bridges the gap between bulk and thin-film diffusion couples in terms of reaction temperatures. The activation energy of NiAl3 growth is 1.2±0.2 eV.