The influence of fine alumina particles on the mechanical properties and thermal shock behaviour of slip-cast alumina-mullite refractories

Abstract

The object of this work is to improve understanding of relationships between microstructure and those mechanical properties likely to affect thermal shock behaviour of slip-cast alumina-mullite refractories. The incorporation of fine grain (similar to5 mum) alumina particles improved both densification and mechanical properties markedly with increasing alumina content. The resistance to fracture initiation and propagation caused by the thermal stresses was increased, as supported by the R and R-st parameters. In addition, there was a marked change in fracture path from mainly intergranular to a significant amount of transgranular fracture with increasing fine alumina particle content. This indicated that more energy was required to initiate crack propagation, associated with the high values of fracture surface energy and fracture toughness. Thermal shock tests confirmed that the strength values were also improved with increasing quench temperature, leading to a high thermal shock resistance of alumina-mullite refractories.