The effect of the degree of long-range order upon the migration energy in NiAl was investigated by using electrical resistivity and X-ray diffraction techniques. The activation energies for the migration of excess vacancies in single crystals were equal to 1.55eV for specimens quenched from 1473K, and equal to 1.40eV for those quenched from 1673K. The degree of long-range order in monocrystalline NiAl, as deduced from the results of Hughes et al., seemed to be consistent with this decreasing trend in activation energy. A reduction in the degree of long-range order explained these variations in migration energy, according to the Girifalco model.

The Effect of Long-Range Order on the Activation Energy for Atomic Migration in NiAl Alloys - Resistivity Study. H.Ko, K.T.Hong, M.J.Kaufmann, K.S.Lee: Journal of Materials Science, 2002, 37[9], 1915-20