Failure Mechanisms in Directionally Solidified Alumina-Titania Composites

The mechanical properties of directionally solidified two-phase eutectics can be superior to that of either constituent alone due to the strong constraining effects of the interlocking microstructure. The present work focuses on the failure mechanisms that occur in Al2O3-Al2TiO5 composites fabricated by directional solidification. Two compositions rich in alumina have been considered. The constituents were the same in both materials, primary Al2O3 dendrites surrounded by a TiO2-containing phase, with different morphological and size characteristics. The dendrites in the material containing the smallest amount of Al2O3 were short and highly interpenetrated by the secondary phase whereas those of the material with the highest Al2O3 content were long and much less interpenetrated. The mechanical behaviour in bending was determined by these microstructural differences because the load bearing phase in these directionally solidified materials in the system Al2O3-Al2TiO5 are the Al2O3 dendrites.