Influence of crystal orientation on mechanical properties and stress distribution in monocrystalline sapphire

Abstract

The deformation behavior of monocrystalline materials is intricately linked to the anisotropic nature of their mechanical characteristics, slip motion, and cleavage motion. To systematically analyze the deformation and fracture behavior of monocrystalline sapphire and address existing shortcomings in the detection of its mechanical properties, we conducted a series of nanoindentation experiments and analyses across various crystal orientations of sapphire. A model for the stress field was developed by considering slip motion, cleavage fracture, and the mechanical properties of monocrystalline sapphire. Our findings indicate that cracks propagate in specific directions and exhibit anisotropic characteristics. The hardness and elastic modulus of sapphire across distinct planes follow the order: R < N < C < M < A, while the fracture toughness exhibits the opposite trend. Results concerning the stress field distribution, Schmid factor, and cleavage factor reveal that the M and A planes are more susceptible to brittle cracking and cleavage fracture, whereas the R and N planes are more likely to undergo plastic deformation.