Interdiffusivity of the NiAl phase in the binary system was estimated, as a function of composition, in NiAl phases formed on pure Ni by using the vapor–solid technique. The calculations indicated that interdiffusivity in the as-formed NiAl phase exhibited a minimum at about 48at%Al; deviating slightly from stoichiometry. This was explained in terms of a concentration dependence of the thermodynamic factor, and the creation of Al-vacancies on the Ni-rich side of stoichiometry. It was observed that the activation energy for interdiffusion in as-formed NiAl was particularly sensitive to the presence of constitutional vacancies, and was probably related to the lattice parameter of the NiAl phase.

Estimation of Interdiffusivity of the NiAl Phase in Ni–Al Binary System. H.Wei, X.Sun, Q.Zheng, H.Guan, Z.Hu: Acta Materialia, 2004, 52[9], 2645-51