Interaction of an edge dislocation with Cu–Ni-vacancy clusters in bcc iron

In this work we studied the interaction of a ½〈1 1 1〉{1 1 0} edge dislocation with Cu-rich precipitates, mimicking those that are known to form in RPV steels. We have applied a combination of Monte Carlo and molecular dynamics techniques to explore the structure and obstacle strength of Cu–Ni-vacancy clusters of nanometric size below the resolution limit of transmission electron microscopy. The results show that the strength of Cu-vacancy, Cu–Ni and Cu–Ni-vacancy clusters is comparable or even smaller than that of pure Cu clusters, but considerably smaller than the strength of pure vacancy clusters or nanovoids. Thus, the enrichment of small Cu precipitates by Ni atoms and/or a small amount of vacancies does not increase their obstacle strength, at least in the case of edge dislocations.