Numerical simulation of thermal residual stress in Mo- and FeAl-toughened Al2O3

Microstructure-level residual stresses occur in composite ceramics during processing, mainly as a result of thermal expansion anisotropy. The magnitude of these stresses can be sufficiently high to cause spontaneous microcracking when cooled from the processing temperature. They are also likely to affect where cracks initiate and propagate under macroscopic loading. Alumina-based composites containing different amount of second phase particles with lower (Mo) and higher thermal expansion coefficient (FeAl) were prepared. Fluorescence spectroscopy was used to measure the residual stress distribution due to thermal expansion anisotropy in these composites. A finite element model was also established for two-phase ceramics. The residual stress distribution in the model was analyzed, and the variation regularity of internal stress along with the second phase particle's volumetric proportion was given.