Al2O3/ZrO2 (Y2O3) PREPARED BY COMBUSTION SYNTHESIS UNDER HIGH GRAVITY

Abstract

By introducing ZrO 2 (4 Y ) powder into the thermit, Al 2 O 3/ ZrO 2 (4 Y ) composite ceramics of different composition and microstructures were prepared through combustion synthesis under high gravity, and the correlations of composition, microstructures and mechanical properties of composite ceramics were investigated. The results of XRD, SEM and EDS showed that Al 2 O 3/33% ZrO 2 (4 Y ) were composed of random-orientated rod-shaped colonies consisting of a triangular dispersion of orderly submicron-nanometer t - ZrO 2 fibers, surrounded by inter-colony regions consisting of spherically-shaped micronmeter t - ZrO 2 grains; meanwhile, Al 2 O 3/45% ZrO 2 (4 Y ) were comprised of spherically-shaped micron-meter t - ZrO 2 grains. Similar to the international directionally solidified Al 2 O 3/ ZrO 2 ( Y 2 O 3), the EDS results also indicated that there are no impurities, amorphous phases and grain boundaries but clean phase interfaces in two ceramic composites. Compared to the international directionally solidified Al 2 O 3/ ZrO 2 ( Y 2 O 3), the increase in hardness and flexural strength of Al 2 O 3/33% ZrO 2 (4 Y ) in the experiment was due to small-size defect and high fracture toughness induced by compressive residual stress effect and transformation toughening mechanisms; meanwhile, high flexural strength of Al 2 O 3/45% ZrO 2 (4 Y ) was considered to be a result of the fine spherically-shaped t - ZrO 2 grains separated from the melt under high gravity, and high fracture toughness induced by transformation toughening and micro-crack toughening mechanisms.