Elastic properties and damping behavior of alumina–zirconia composites at room temperature

Alumina–zirconia composite ceramics (AZ composites) have been prepared in the whole range of compositions from pure alumina to zirconia (in steps of 10 vol.%) by slip casting, followed by sintering at 1350 °C and microstructural characterization via the Archimedes method (relative densities 0.93–0.99). Young's modulus has been measured at room temperature via the impulse excitation technique (IET) and, after appropriate porosity correction (linear, power-law, exponential), found to be in good agreement with the Hashin–Shtrikman bounds. The damping factor (internal friction), which has been measured for dense AZ composites (also via IET at room temperature), is found to increase with increasing zirconia content. Damping factors measured for porous AZ composites with porosities 25–71%, prepared with corn starch as a pore former, have been found to depend only slightly on porosity, unless the porosities are extremely high (>70%). At these porosities, however, where the Young's moduli approach zero, the damping factors exhibit a steep increase.