Thermal-elastic response of marble polycrystals: Influence of grain orientation configuration

摘要

Two-dimensional, microstructure-based finite element simulations were used to elucidate the influence of grain orientation configuration on the thermal-elastic response of poly-crystalline ceramic materials. The two main constituent minerals of marbles, calcite and dolomite, were considered. The crystallographic configuration of the grains is described in terms of the distribution of grain orientations and grain-boundary misorientations. To probe the influence of grain orientation configuration, we first generated the geometry of a hypothetical microstructure. Next, crystallographic orientations were assigned to each grain in the microstructure such that the grain orientations and grain-boundary misorientations matched predefined distributions. By varying the predefined distributions, we generated 45 unique microstructures covering a wide range of crystallographic configurations. After assigning thermal-elastic properties to each structure, corresponding to either calcite or dolomite, finite-element simulations were performed. The simulations demonstrated that both the orientation and misorientation distributions have a substantial impact on the thermal-elastic response of microstructures with the same material properties: varying the crystallographic configuration results in variations of stored elastic strain energy density from 10 kJ m~3 to 39 kJ m{sup}(-3) for a 100 ℃ temperature change. Further, the ratio of the bulk coefficient of thermal expansion in the two principal directions varies from -0.17 to 1.46. Surprisingly, the grain-boundary misorientations alone had a substantial impact on the thermal-elastic response of the system. By simply rearranging a fixed set of crystallographic orientations to obtain different nearest-neighbor misorientation configurations, we observed variations in strain energy density from 10 kJ m{sup}(-3) to 39 kJ m{sup}(-3) and variations in thermal expansion ratio from 0.06 to 0.90. The results suggest that to predict accurately the thermal-elastic response of polycrys-talline ceramics, it is critical to consider both the distribution of grain-boundary misorientations as well as the distribution of grain orientations.