Modeling brittle fracture due to anisotropic thermal expansion in polycrystalline materials

•Investigated the fracture of α-uranium polycrystals due to anisotropic thermal expansion.•Cooling resulted in severe fracture due to the larger anisotropy at elevated temperatures.•The total crack surface area decreased with decreasing grain misorientation.•The thermal expansion in the [010] direction was the primary cause for fracture. This work investigated brittle fracture of polycrystalline materials due to thermal stresses arising from anisotropic thermal expansion. We used phase-field fracture simulations with the properties of α-uranium (α-U) and assumed a linear elastic mechanical response. Three-dimensional simulations were used to predict fracture for various conditions and crystallographic textures. We found that fracture was more pronounced during cooling than during heating because the anisotropy increased with temperature. We also found that the total crack surface area increased with increasing average misorientation, while the net shape change of the material decreased with increasing misorientation. Two-dimensional simulations in which one crystallographic coefficient of thermal expansion (CTE) was set to zero indicated that the largest difference between the CTE in the three crystallographic directions dominates the fracture.