The reaction mechanism analysis and mechanical properties of large-size Al₂O₃/ZrO₂ eutectic ceramics prepared by a novel combustion synthesis

Large-size Al₂O₃/ZrO₂ eutectic ceramics (Φ53 × 75 mm) were successfully fabricated based on the exothermic reaction between Al and Zr(NO₃)₄ via a novel combustion synthesis under low pressure. The reaction mechanism was analyzed using the thermodynamics method. In the reaction process, the intermediate products of AlN were partially converted into ZrN phase, and the remaining AlN phase decomposed into nitrogen. The Al₂O₃/ZrO₂ composite materials with 85.74 vol% eutectic were obtained with the mole ratio of ZrO₂:Al₂O₃ reached 0.9:1. The rod-like ZrO₂ phase with a diameter ~ 268 nm was in-situ embedded in Al₂O₃ phase; the average eutectic interspacing is ~ 183 nm, and the average width of grain boundary is 520 nm. The hardness and fracture toughness of Al₂O₃/ZrO₂ eutectic ceramics are 17.8 GPa and 10.6 MPa m^1/2, respectively. The excellent mechanical properties are ascribed to the fine microstructure and special phase composition.