The segregation behavior of manganese and silicon at the coherent interfaces of copper precipitates in ferritic steels

We have performed first-principles calculations to study the segregation behavior of Mn and Si at the interfaces of Cu precipitates in ferritic steels. We find that both the segregation energies of substitutional Mn and Si at the interfaces of the Cu precipitates are negligible. However, the energetics indicate that the self-interstitial dumbbells containing Mn or Si (Mn@SI or Si@SI)1 nterstitial dumbbells containing Mn or Si, Mn@SI or Si@SI; self-interstitial, SI; reactor pressure vessel, RPV; ductile to brittle transition temperature, DBTT. he coherent interface of Fe/Cu is more favorable than the Mn@SI or Si@SI embodied in pure Fe or Cu phases, respectively. The relative stability of the substitutional defects, Mn@SI, Si@SI, and pure Fe self-interstitial (SI) dumbbells can well account for the difference in segregation behavior of Mn and Si at Cu precipitates in the ferritic steels under the condition of irradiation and thermal aging. Furthermore, we find that both the Mn@SI and Si@SI segregation result an embrittlement trend on the interfaces of Cu precipitates in ferritic steels.