UO₂ Grain Growth: Developing Phase Field Models for Pore Dragging, Solute Dragging and Anisotropic Grain Boundary Energies

Technical Report · Wed Sep 28 04:00:00 EDT 2016

DOI:https://doi.org/10.2172/1360119· OSTI ID:1360119

Ahmed, K. ^[1]; Tonks, M. ^[1]; Zhang, Y. ^[1]; Biner, B. ^[1]

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1. Idaho National Lab. (INL), Idaho Falls, ID (United States)

A detailed phase field model for the effect of pore drag on grain growth kinetics was implemented in MARMOT. The model takes into consideration both the curvature-driven grain boundary motion and pore migration by surface diffusion. As such, the model accounts for the interaction between pore and grain boundary kinetics, which tends to retard the grain growth process. Our 2D and 3D simulations demonstrate that the model capture all possible pore-grain boundary interactions proposed in theoretical models. For high enough surface mobility, the pores move along with the migrating boundary as a quasi-rigid-body, albeit hindering its migration rate compared to the pore-free case. For less mobile pores, the migrating boundary can separate from the pores. For the pore-controlled grain growth kinetics, the model predicts a strong dependence of the growth rate on the number of pores, pore size, and surface diffusivity in agreement with theroretical models. An evolution equation for the grain size that includes these parameters was derived and showed to agree well with numerical solution. It shows a smooth transition from boundary-controlled kinetics to pore-controlled kinetics as the surface diffusivity decreases or the number of pores or their size increases. This equation can be utilized in BISON to give accurate estimate for the grain size evolution. This will be accomplished in the near future. The effect of solute drag and anisotropy of grain boundary on grain growth will be investigated in future studies.

• Research Organization: Idaho National Laboratory, Idaho Falls, ID (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE)
• DOE Contract Number: AC07-05ID14517
• OSTI ID: 1360119
• Report Number(s): INL/EXT--16-39965
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
GRAIN BOUNDARIES
GRAIN GROWTH
GRAIN SIZE
URANIUM DIOXIDE
grain growth