Fracture Induced in Al 2 O 3 Bicrystals by Anisotropic Thermal Expansion

Bicrystals of Al 2 O 3 were fabricated to study the effects of thermal expansion anisotropy on fracture in a model system containing one grain boundary. Fractures occurred perpendicular to the directions of maximum tensile stress in bicrystals with thermal expansion coefficient differences as low as 0.31×10 −60 C −1 and originated at the boundary, probably in areas of high residual stress associated with pores. Numerical stress analysis of two‐dimensional model bicrystal configurations showed that stresses induced by thermal expansion anisotropy are maximal in a region localized along the bicrystal boundary.