Reduction of defect generation and development of sinks at nanocluster boundary in oxide dispersion-strengthened steel
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abstract
The radiation resistance mechanisms of nanoclusters (NCs) in oxide dispersion-strengthened (ODS) steels have been investigated. Molecular dynamics simulation has been used to investigate defect generation during the primary damage state of a displacement cascade in ODS steels for NCs of various radii and a range of primary knock-on atom (PKA) energies. Y2O3 NCs considerably enhance the radiation resistance of ODS steels by reducing the peak defect generation during the cascade within the Fe matrix. The NC also affects the morphology of the collision cascades, depending on PKA energy. At lower energies, the NCs outer circumference act as a cessation point forming a dampened shockwave compared to a pure Fe system. At higher energies, the PKA energy is able to transfer through the NC, thus causing two smaller shockwaves in the Fe matrix. Along with the alteration of the cascade morphology, the NC boundary acts as a strong defect sink to absorb defects and defect clusters, leading to significant recombination of interstitials and vacancies away from the NC. The interfacial energy of the NCs with the Fe matrix increases with increasing diameter of the oxide NCs. The evolution of the NC is tracked through the primary damage state of a cascade, and the effects of ballistic dissolution play a key role in this evolution, most evident in the 2nm NC.
