Atomistic simulation of Cu-Ni precipitates hardening in alpha-iron

摘要

In this paper, we investigated the interaction of an edge dislocation with Cu precipitates with a spherical geometry and with Cu-Ni precipitates that possess a Cu core with an outer Ni shell, commonly observed in reactor pressure vessel (RPV) steels. We applied molecular dynamics techniques to explore the critical stress required to unpin the dislocation (CSRUD), the breakaway dislocation line shape when the dislocation leaves the precipitates and the transition of Cu atoms within precipitates. The results indicate that the CSRUD of the Cu-Ni precipitates with a diameter less than 2.38 nm is larger than that of Cu precipitates that contain the same number of Cu atoms, while for a diameter larger than 2.38 nm, the CSRUD of Cu-Ni precipitates is weaker, which is related to the bcc to fcc-like or hcp-like atoms transformation in precipitates. The dislocations interact with Cu and Cu-Ni precipitates via the cut mechanism.