Processing and mechanical properties of textured mullite/zirconia composites

Textured mullite/zirconia (ZrO2) composites were prepared from a reactive mixture of alumina (Al2O3) and zircon (ZrSiO4) powders together with acicular aluminum borate templates to nucleate and texture mullite grains in the [0 0 1]. Effect of texturing on Youngʹs modulus and strength is investigated by fabricating samples with varying degree of grain orientation by templated grain growth (TGG). It is found that both Youngʹs modulus and strength increases with a better orientation control of mullite grains in the longitudinal direction. The increase in Youngʹs modulus is consistent with the anisotropic elastic properties of mullite crystal. The increase in strength is attributed to the fact that pores are smaller and elongated in the texture direction resulting in smaller defect size. Scanning electron microscopy (SEM) observations indicate that crack propagation at mullite crystals is transgranular.