Al2O3-ZrO2 (Y2O3) Eutectic Ceramics Preparing by Self-Pressing Assisting Combustion Synthesis under High Gravity

By self-pressing assisting combustion synthesis under high gravity to avoid bulk solidification of the ceramic melt in closed space, large bulk Al2O3-ZrO2(Y2O3) eutectic ceramics without the shrinkage cavities were achieved. XRD, SEM and EDS results show the eutectic ceramics are composed of alpha-Al2O3, t-ZrO2 and a few m-ZrO2 phases. As the self-pressing force increases, the transformable t-ZrO2 increases in the ceramics, and the ceramic matrix consisting of rod-shaped eutectic colonies is refined, followed by the increase of the volume fraction and the average aspect ratio of the colonies, whereas the irregular ZrO2 crystals around the colonies gradually develop fine t-ZrO2 spherical crystals, leading to the increases in flexural strength, Vickers hardness and fracture toughness of the ceramics. When the self-pressing force reaches 0.8 MPa under high gravity of 200 g (g is the acceleration of gravity, i.e. 9.8 m.s(-2)), the maximum values in mechanical properties of flexural strength (1050 +/- 105) MPa, Vickers hardness (17.8 +/- 1.5) GPa and fracture toughness (14.2 +/- 1.0) MPa.m(1/2) are achieved simultaneously.