Effects of microstructures on the fracture properties of silicon nitride ceramics at elevated temperatures

Abstract

Ceramic components often fail by a brittle fracture mode during the service process. Various factors can affect the fracture properties of ceramics. Experimental methods are usually used to investigate fracture behaviors. However, they give a composite result and the contribution to fracture from each factor is not clear. In the present work, a micromechanical model is developed to quantitatively characterize the fracture properties of ceramics at elevated temperatures. The control method for the microstructures of ceramics is proposed based on the Voronoi diagram. The temperature-dependent surface energy model of ceramics is revised by considering the effects of thermal decomposition and phase transformation. The interface energies at different temperatures are obtained by the inversion method. The criterion for crack propagation of ceramics at elevated temperatures is developed based on the G-criterion. The effects of temperature, grain size, grain size distribution, and grain boundary phase thickness on the fracture behaviors of silicon nitride are studied numerically.