Iron-copper-nickel many-body potential consistent with thermodynamics

The Fe-Cu-Ni ternary alloy is of interest for nuclear applications because Cu and Ni are considered to have major effects on the embrittlement under irradiation of reactor pressure vessel steels. To improve our understanding on this phenomenon, large scale atomistic simulations in this model alloy are desirable. For this purpose we develop a ternary Fe-Cu-Ni many-body potential consistent with thermodynamics is developed for the first time. The potential was validated using molecular static and atomistic kinetic Monte Carlo simulations and a qualitative agreement with experiments was established. In particular, Cu precipitates were found to be enriched by Ni on the precipitate surface. Also, the effects diluting the Fe-Cu alloy by Ni on mean precipitate size and density showed similar trends as observed in experiments; i.e. no effect of Ni on the mean precipitate size and an increase in the maximum precipitate density due to the addition of Ni. In absolute terms, agreement with experiment is poor due to the limited box size used in the simulations, as correspondingly discussed.