[SY-B10] Symposium B-10

[SY-B10] Modelling swelling and growth under irradiation using the phase field method

^○Daniel Schwen, Andea M. Jokisaari (Dept. of Fuels Modeling and Simulation, Idaho National Laboratory, United States of America)

In extreme environments with high point defect production rates, some materials can experience macroscopic dimensional changes due to the mechanisms of swelling and growth. Both processes are related to preferential absorption of different point defect species at different sinks. In the case of swelling this entails the creation of voids which act as vacancy sinks, while interstitials are absorbed at dislocations or grain boundaries where new lattice sites are created, leading to a total volume increase of the sample. Growth occurs if anisotropic interstitial and vacancy fluxes with differing spatial orientations lead to lattice site creation and removal along non-parallel lattice planes, leading to a volume conserving shape change. Prediction of swelling and growth behavior requires an understanding of the defect transport and reaction processes at the mesoscale. The phase field method has been established as a standard modeling technique on these length scales.

In this work we develop a modified set of phase field equations that allow for the local and anisotropic creation and destruction of lattice sites at sinks using a tensor field describing the local lattice site changes. We apply this method to study the effects of microstructure on swelling and growth behavior in polycrystalline materials, in the presence of applied mechanical loading, and microstructural features such as precipitates.