Ceramics-Silikáty 49, (2) 77 - 85 (2005)

In this fifth and last paper of a series on the effective elastic properties of alumina-zirconia composite ceramics (AZ composites) the tensile moduli of dense and porous AZ composites are investigated from the theoretical point of view and compared with experimental data. For dense AZ composites the Hashin-Shtrikman bounds turn out to be sufficiently close to each other and excellent agreement is found between theoretically predicted and measured values, so that the arithmetic HashinShtrikman average can be used for predicting effective elastic moduli for arbitrary compositions. For dense zirconia-toughened alumina (ZTA) with 15 wt.% and dense alumina-containing tetragonal zirconia (ATZ) with 80 wt.% of zirconia the theoretically predicted effective tensile moduli are 375 GPa and 251 GPa, respectively. For porous AZ composites (prepared by starch consolidation casting) the consistency of the experimentally measured data is assessed with regard to the HashinShtrikman upper bound. Fitting results confirm the superiority of the new relation E/E₀ = (1 - Φ)·(1 - Φ/Φ_C), where E is the effective tensile modulus and Φ the porosity, over most other fit models. Extrapolated E₀ values are 351 GPa and 237 GPa and critical porosities Φ_C are 0.796 and 0.882 for porous ZTA and ATZ, respectively.