A Study on Strength Anisotropy and the Peculiarity of the Fracture Origin of HP-Si₃N₄

Abstract

The anisotropic mechanical properties were studied in uniaxially hot-pressed silicon nitride. The flexural strength and Weibull modulus of specimens with longitudinal direction perpendicular to the hot-pressing direction were 22% and 38% higher than those of parallel specimens, respectively. The perpendicular specimens had narrower distributions of defect size and 20% higher critical rupture stress for the apparent same-sized defects than the parallel ones. These differences have been attributed to the shape and orientation of defects.