Positron Annihilation and TEM Characterization of Cu-Enriched Clusters in the Ferritic Steels Containing Copper

摘要

Nanosized Cu-enriched clusters formed in Cu-containing reactor pressure vessel (RPV) steels during service have a deleterious effect on mechanical properties, which can result in RPV embrittlement and limit reactor operation life. To understand the effect of Cu-enriched clusters (CECs) behavior on mechanical properties, thermal aging at 370℃ for times up to 13200 h was performed on the high-copper ferritic steels. The microstructure evolution of CECs was investigated by positron annihilation spectroscopy (PAS) and transmission electron microscope (TEM). The results show that the CECs formed after aging times up to 3000 h, which composition is composed of Fe, Cu, Ni, Mn, and Si, are 9R structures. The CECs lead to precipitation hardening/embrittlement effects. The changes of hardness have a linear relationship with transition temperature shifts.