The effect of mullite on the mechanical properties and thermal shock behaviour of alumina–mullite refractory materials

Mechanical properties and thermal shock behaviour of slip-cast alumina-mullite refractories have been investigated. There was a marked improvement in strength, Youngʹs modulus and fracture toughness values with the addition of finest (∼5 μm) mullite particles. The shorter length needle-like mullite particles led to some pull-out and crack deflection. More fracture surface energy was therefore required to connect the cracks for propagation, resulting in a high value of fracture toughness. The resistance to fracture initiation and propagation caused by the thermal stresses was increased, as supported by the R and Rst parameters. Therefore, the retained strength was improved by increasing the quench temperature, showing a high resistance to thermal shock.