The microstructure, formation mechanism and sintering characteristics of Al2O3/ZrO2 supersaturated solid solution powders

In this study, the Al2O3/ZrO2 supersaturated solid solution powders with different ZrO2 contents were successfully synthesized by a novel combustion synthesis combined with water cooling (CS-WC) method. The solid solubility and formation mechanism of solid solution under the extremely non-equilibrium solidification condition were discussed in details. The ultra-high cooling rate greatly improves the solubility limit of Al2O3 in ZrO2. When ZrO2 content is 30 mol%, the Al2O3 has been almost dissolved into the ZrO2 lattice. The formation mechanism of solid solution can be attributed to solute interception caused by the huge degree of supercooling. During the sintering process, the solid solution powders precipitate ZrO2 particles and the Al2O3 matrix, which forms a fine and uniform nanostructure. Due to the synergistic effect of t-m phase transformation toughening and ZrO2 nanoparticles toughening, the Al2O3/ZrO2 nanoceramics exhibit excellent mechanical properties when ZrO2 contents are at the range of 25-37 mol%.