He bubble growth in nickel simulated by object kinetic Monte Carlo

Abstract

When Ni-based alloys are exposed to neutron irradiation, (n,α) transmutation introduces helium to the metal, leading to the formation of bubbles, which can severely affect the properties of the material. Identifying the key parameters controlling bubble growth can help us design materials with improved radiation tolerance. In this study, we parameterized an object kinetic Monte Carlo (OkMC) framework able to simulate the coalescence and growth of helium bubbles in pure Ni during and after helium ion implantation. The simulated bubbles size is consistent with phenomenological models based on past experimental studies. Our simulations indicate that the mean He bubble size is strongly correlated with temperature and inversely correlated with the implantation dose rate. The interactions between irradiation-induced defects and interfaces (sinks) are shown to play a key role in determining the size and stability of bubbles. Furthermore, our simulations suggest that the controlling reaction in swelling is the annihilation of self-interstitial defects at sinks, not the presence of He.