Direct measurements of thermal and radiation-enhanced diffusion were made, above and below the ordering temperature of this L12-structured metal, by using Ni and Pd impurity tracers to simulate the diffusion of Cu and Au, respectively (figure 7). The apparent activation enthalpies were obtained for these 2 tracers, above and below the ordering temperature. Both diffusion coefficients were found to decrease significantly upon ordering, by factors of 2 and 4 for thermal and radiation-enhanced diffusion, respectively. The results indicated that the contribution which was made by interstitial atoms to the radiation-enhanced diffusion of Ni and Pd could be negligible.

Y.S.Lee, R.S.Averback, C.P.Flynn: Philosophical Magazine Letters, 1994, 70[5], 269-76