Temperature dependence of constitutive behaviour for solid-state sintering of alumina Original Research Article

A discontinuous hot forging approach was employed in this study in order to extract the temperature dependence of the constitutive sintering parameters for alumina. Uniaxial viscosity and sintering stress were both experimentally obtained as functions of density and temperature for an isotropic microstructure. The activation energy for the viscosities was determined to be approximately 480 kJ/mol by means of an Arrhenius-type plot incorporating the grain size data at varying temperatures. It was indicated that creep and densification during sintering of alumina under a small uniaxial load were both grain boundary diffusion controlled kinetic processes. The same temperature dependence of uniaxial and bulk viscosities was demonstrated, indicating that the viscous Poissonʹs coefficient is temperature-independent. The sintering stress of a porous compact was experimentally identified as independent of temperature, but inversely proportional to grain size, in agreement with theoretical predictions.