Theoretical and experimental analyses of Young's modulus and thermal expansion coefficient of the alumina-mullite system

Young's moduli (E) and thermal expansion coefficients (TECs) of the alumina-mullite-pore system (96.4-99.5% relative density) were measured for a wide mullite fraction range from 0 to 100 vol%. Both E and TEC values decreased at high mullite fractions. These properties were theoretically analyzed with four proposed model structures that were constructed by three-phase systems of mullite (or alumina) continuous phase 2-pore dispersed phase 1-alumina (or mullite) dispersed phase 3. The ratios of E(theoretical)/E(experimental) and TEC(theoretical)/TEC(experimental) were very close to unity, depending on the mullite fraction. That is, the measured E and TEC values are closely related to the change in the composite microstructure as a function of mullite fraction.