Radiation enhanced copper clustering processes in Fe–Cu alloys during electron and ion irradiations as measured by electrical resistivity

Abstract

To study the mechanism of radiation-enhanced clustering of copper atoms in Fe–Cu alloys, in situ electrical resistivity measurements are performed during irradiation with 100 MeV carbon ions and with 2 MeV electrons at 300 K. Two kinds of highly pure Fe–Cu alloys with Cu content of 0.02 and 0.6 wt% are used. The results are summarized as follows: (1) Although there is a steep initial resistivity increase below about 10 μdpa, the resistivity steadily decreases after this initial transient in Fe–0.6wt%Cu alloy, while in Fe–0.02wt%Cu alloy, the resistivity either decreases slowly or stays almost constant. The rate of change in resistivity depends on copper concentration. (2) The rate of change in resistivity per dpa is larger for electron irradiation than for ion irradiation. (3) Change in dose rate from 10 −8 to 10 −9 dpa/s slightly enhances the rate of resistivity change per dpa. The decrease in resistivity with dose is considered to be due to clustering or precipitation of copper atoms. The initial abrupt increase in resistivity is too large to be accounted for by initial introduction of point defects before copper clustering. Tentatively the phenomenon is explained as due to the formation of embryos of copper precipitates with a large strain field around them. Quantitative evaluation of the results using resistivity contribution of a unit concentration of Frenkel pairs and that of copper atoms gives an important conclusion that more than one copper atom are removed from solid solution by one Frenkel pair. The clustering efficiency is surprisingly high in the present case compared with the ordinary radiation-induced or radiation-enhanced precipitation processes.