Modelling of Oxide Dispersion Strengthened Fe alloys with Kinetic Monte Carlo simulation supported by DFT calculations


Modelling of Oxide Dispersion Strengthened Fe alloys with Kinetic Monte Carlo simulation supported by DFT calculations

Liedke, B.; Posselt, M.; Murali, D.; Claisse, A.; Olsson, P.

Abstract

Oxide Dispersion Strengthened (ODS) steels are considered as one of the most promising candidates for structural materials in next generation nuclear fusion reactors and future nuclear fission reactors [1]. The ODS materials consist of a ferritic or ferritic/martensitic Fe-Cr matrix filled with yttria-based oxide particles and is fabricated during mechanical alloying and hot consolidation processes. It is well known that their extraordinary properties such as high-temperature creep strength as well as high dose ion/neutron irradiation resistance are due to formation of small Y-Ti-O clusters with a size of few nanometers. Besides their significant effect on reduction of dislocations and grain-boundaries mobility, the nanoclusters also act as traps for point defects like vacancies, interstitials and helium, which may be typically generated in a nuclear reactor. It is still under debate what the formation mechanisms of the nanoclusters are and why they prove such high temperature and radiation damage stability.
Experimental methods typically applied to investigate the issues stated above cannot fully reflect the atomic-scale of the nanoclusters, as well as the mechanisms related to their formation, evolution and destruction upon radiation damage. Therefore, atomistic computer experiments can significantly contribute to a general understanding.
In this work, kinetic Monte Carlo (KMC) technique is applied to study evolution of Y-Ti-O nanoclusters in a bcc-Fe and FeCr matrix. Starting from a uniform distribution of O, Y, Ti atoms in the matrix at first a stationary state is produced by high temperature annealing. Such a state is characterized by a certain population of Y-Ti-O nanoclusters. Then vacancies and interstitials are introduced in order to simulate ion and neutron irradiation taking into account realistic conditions, and the evolution of the nanostructure is studied. The parameters for the atomic interactions used in KMC were obtained recently by first-principle Density-Functional-Theory calculations and applied in Metropolis Monte Carlo simulations on energetics, structure and composition of the Y-Ti-O nanoclusters [2].
1. G. R. Odette, M. J. Alinger, B. D. Wirth, Annu. Rev. Mater. Res. 38, 471 (2008)
2. M. Posselt, D. Murali, B. K. Panigrahi, Modelling Simul. Mater. Sci. Eng. 22, 085003 (2014)

Keywords: ODS alloys; DFT; KMC; atomistic modelling; radiation damage

  • Lecture (Conference)
    3rd ODISSEUS Workshop, 19.-20.04.2016, HZDR, Germany

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