Stress state and fracture behavior of alumina–mullite intragranular particulate composites

We investigated the fracture behavior of intragranular particle-reinforced alumina–mullite composites in terms of the effect of inter-phase microstresses on grain and grain boundary toughness. First, we calculated the residual matrix microstresses in the composites and validated the results by experimental measurement. Then, we analyzed the influence of the stress state on crack propagating and calculated the ratios of grain boundary toughness to grain toughness and deduced the percentage of transgranular fracture (PTF) that increases with the matrix microstress increase. On basis of the above results, we established the relationship between the microstructural features, matrix microstresses, and PTF. The results agree qualitatively with the experimental observations. Finally, we interpreted the strengthening mechanism and explained the excellent wear resistance of the alumina–mullite composites in terms of fracture-mode transition.