The activation energy for loop growth in Cu and in Cu-Ni alloys

The apparent activation energy for the growth of interstitial dislocation loops in copper, Cu-l%Ni, Cu-2%Ni, and Cu-5%Ni during high voltage electron microscope irradiation was determined. The apparent activation energy for loop growth in all these materials can be taken to be 0.34eV±0.02eV. This value together with the corresponding value of 0.44eV±0.02eV determined earlier for Cu-10%Ni is discussed with reference to the void growth rates observed
in these materials. The apparent activationenergy for loop growth in copper (and in Cu-l%Ni that has a void growth rate similar to that in pure copper) is interpreted as twice the vacancy migration energy (indicating that divacancies do
not play any significant role). For the materials with higher Ni content (in which the void growth rate is much lower than that in Cu and Cu-l%Ni) the measured apparent activation energy is interpreted to be characteristic of loops positioned fairly close to the foil surface and not of loops in "bulk material". Prom the present results in combination with the earlier results for Cu-10%Ni it is concluded that interstitial trapping is the most likely explanation of the reduced void growth rate in Cu-Ni alloys.