A three-scale homogenisation approach to the prediction of long-time absorption of radiation induced interstitials by nanovoids at interfaces

Various nanoscale materials that contain high density of interfaces highlight an optimistic perspective of discovering radiation tolerant materials. However, given the huge dimensional contrast between the core structural components of nuclear reactors and many nanoscale treatments for improving materials radiation resistance, the corresponding predictive models are required to possess a delicate balance between resolution and efficiency. Motivated by this, a three-scale homogenisation scheme is introduced in this article, and a continuum model for the long-time interstitial-sink behaviour at interfaces is derived with all important nanoscopic parameters and mechanisms properly retained. Compared with the existing works alike, the derived model shows its advantage in at least two aspects. First, it incorporates the collective effect of multiple sinks on interstitial migration which is not fully taken into account in conventional works, and the accuracy of the continuum description to the underlying mechanisms is thus improved substantially. Second, the derived model naturally formulates a sink saturation condition under which sinks no longer absorb point defects. The present work originates from developing a long-time predictive model for a recent proposal for improving the radiation tolerance of materials by Chen et al. (2015), and the derived three-scale homogenisation approach can be naturally generalised to model the collective behaviour of other types of sink-defect interactions.