Visco-elasticity in alumina ceramics at room temperature

The decrease in the fracture strength of alumina ceramics at room temperature has usually been assumed to be caused by the effect of stress corrosion. However, at high temperatures, a viscous deformation will occur due to a glass-like phase which exists in the grain boundary. A study of the relation of the fracture strength of an alumina ceramics smooth specimen at room temperature to the visco-elastic property was performed. Mechanical tests and visco-elastic analysis, has shown that the fracture strength of this kind is controlled by the visco-elasticity.