High temperature mechanical behavior of aluminium titanate-mullite composites

Compressive deformation tests at high temperatures (1300-1450 degreesC) have been performed on aluminium titanate (undoped and modified with MgO and Fe2O3)-10 wt.% mullite composites obtained by reaction sintering. Two deformation regimes have been observed, depending on the experimental conditions. At high stresses/strain rates, the samples failed intergranularly at very small failure strains. At low stresses/strain rates, large macroscopic strains were reached without significant microstructural changes. MgO and Fe2O3 additions have a pronounced effect on the brittle-ductile transition. In contrast, they have no effect on the steady-state flow, which is characterized by a stress exponent close to unity and an activation energy of 650 kJ/mol. Experimental results are compatible with a mechanism of grain boundary sliding controlled by cation bulk diffusion. (C) 2000 Elsevier Science Ltd. All rights reserved.