Kinetic Monte Carlo modelling of Helium Bubble Nucleation onto Oxides in the Fe-Ti-Y-O System

TL;DR

This paper presents a Kinetic Monte Carlo model simulating helium bubble nucleation in ferritic alloys, highlighting the role of Y-Ti-O nano-oxides in trapping helium and preventing bubble formation at grain boundaries.

Contribution

The study introduces a novel KMC model that captures helium behavior and bubble formation in NFAs, emphasizing the effectiveness of nano-oxides in helium management.

Findings

Nano-oxides effectively trap He atoms, reducing bubble formation.

Bubbles prefer the <111> oxide interface as nucleation sites.

Stable bubbles have a He/Vac ratio between 1.3 and 1.8.

Abstract

A Kinetic Monte Carlo (KMC) model was created to simulate the insertion of transmutation He atoms into nanostructured ferritic alloys (NFAs) under neutron irradiation. Interstitial He atoms migrate through the NFA until becoming trapped in bubbles of other He atoms and vacancies created from irradiation. The Y-Ti-O nano-oxides in the NFAs were found to be effective in capturing these He atoms and preventing bubbles from forming at the grain boundary and appear to replicate the characteristics (size and number density) observed in other experiments. The bubbles were found to prefer the <111> oxide interface as a nucleation site and the stable bubbles have a He/Vac ratio between 1.3 and 1.8 He/Vac. The influence of He bubbles on the segregation of solutes to the grain boundaries or on the stability of the nano-oxides were negligible.