Stability and mobility of small vacancy–solute complexes in Fe–MnNi and dilute Fe–X alloys: A kinetic Monte Carlo study

Abstract

a b s t r a c tManganese and nickel solute atoms in irradiated ferritic steels play a major role in the nanostructural evolution of reactor pressure vessels (RPV), as they are responsible for the formation of embrittling nanofeatures even in the absence of copper. The stability and mobility of small vacancy-solute clusters is here studied with an atomistic kinetic Monte Carlo approach based on ab initio calculations, in order to investigate the influence of Mn and Ni on the early life of small radiation-induced vacancy clusters, and to provide the necessary parameters for advanced object kinetic Monte Carlo simulations of the RPV longterm nanostructural evolution. Migration barriers are obtained by direct ab initio calculations or through a binding energy model based on ab initio data. Our results show a clear immobilizing and stabilizing effect on vacancy clusters as the solute content is increased, whereas the only evident difference between the two solute species is a somewhat longer elongation of the cluster mean free path in the presence of a few Mn atoms.

Nanostructure evolution under irradiation in FeMnNi alloys: A “grey alloy” object kinetic Monte Carlo model

“…One might finally argue, however, that the tendency of Cu to precipitate in Fe will soon remove all Cu from the matrix (a small concentration, anyway), whereas Ni and Mn will remain more uniformly distributed in the matrix, thereby producing only noncompact complexes with vacancies and being more efficient in reducing their mobility: specific atomistic studies similar to those in [51], with suitable parameterization, should be performed to clarify this point. Preliminary results have been obtained in [52]. Another possibility is that C might be playing a role.…”

Solute diffusion by self-interstitial defects and radiation-induced segregation in ferritic Fe–X (X=Cr, Cu, Mn, Ni, P, Si) dilute alloys

“…The MFP for 3-dimensional migration is then given by ∆R = √ 6M τ. The results of the Arrhenius fitting in the range 300-1000 K are reported in Table 3, and the MFPs in and under slightly different assumptions [88]. In this sense, KineCluE represents a computationally efficient alternative method to AKMC to paremeterize coarse-grained simulations, which can be especially useful at low temperatures and in the presence of trapping configurations.…”

Density functional theory study of the magnetic moment of solute Mn in bcc Fe

“…Vacancy-solute clusters are a documented phenomenon 59,60 and the binding of solute atoms to vacancies in -Fe is important for understanding solute partitioning, diffusivity and precipitation [61][62][63] . In Figure 9(A-C), the resultant magnetic moment, binding energy and vacancy formation energy of Mn substitution are shown as a function of distance from a vacancy from 1 st  6 th nn.…”