CHARACTERIZATION OF THE ANISOTROPIC GRAIN COARSENING IN ALUMINIUM TITANATE CERAMIC

摘要

A better understanding of the relationship between microstructure of polycrystalline materials and their mechanical properties is required in order to develop refractories with a high level of flexibility (improvement of thermal shock resistance). Aluminum titanate is a suitable ceramic to acquire basic knowledge since firstly, its orthorhombic structure involves needle-type grains which act as fibers in the microstructure and secondly, its large difference in coefficients of thermal expansion along its crystal axes leads to a massive microcracking network occurrence during cooling. These characteristics are of prime importance to explain the enhancement of the non-linearity of the stress-strain law leading to the increase of the strain-to-rupture during thermomechanical loading. All these features are favorable to improve thermal shock resistance. This obtained flexibility authorizes more freedom for the motion process between the grains. Thanks to the analysis of a single crystal by XRD, the structure of the unit cell has been characterized and the direction of single crystal coarsening has been correlated to the crystallographic axis. In particular, the elongated direction of the grain corresponds to the grain oriented along the a axis. This orientation of elongated grain of aluminum titanate has also been confirmed thanks to EBSD characterization.