Papers by Keyword: Al₂O₃/ZrO₂ (Y₂O₃) Composite

Abstract: Based on preparing the large-bulk solidified Al2O3-ZrO2 (Y2O3) ceramic composites by combustion synthesis under high gravity, the solidification behavior and microstructure transformation of the ceramics as well as their effects on the ceramic properties were investigated. XRD, SEM and EDS analyses showed the ceramic microstructures were composed of the irregular eutectics at the surface and the tetragonal ZrO2 micrometer spherical crystals in the center of the ceramics respectively. By combining with irreversible nucleation theory, it is considered that the formation of irregular eutectics with micro-nanocrystalline microstructures is a result of the leading nucleation of Al2O3 high-fusion-entropy phases followed by the coupled growth of Al2O3-ZrO2 phases, whereas the presence of the tetragonal ZrO2 spherical microstructures in the center of the ceramics results from the leading nucleation of ZrO2 cubic phases followed by the independent growth of Al2O3-ZrO2 phases. As a result, it is just the unique microstructure transformation during the solidification process that the highest hardness at the surface and the highest fracture toughness in the center of the ceramics are achieved respectively.

Abstract: Based on preparation of Al2O3/ZrO2 (4Y) by combustion synthesis in high-gravity field, the microstructure transformation and properties of the materials are investigated through adjusting the ZrO2 (4Y) content in the composites. As the content of ZrO2 changed from 37% to 40%, the microstructures of the ceramics transformed the sphere-like tetragonal ZrO2 crystals from the rod-shaped colonies with nanocrystalline structures. Al2O3/33%ZrO2 (4Y) had the maximum relative density, hardness and flexural strength due to the low solidification temperature, the highest volume fraction of the colonies, small-size defect and high fracture toughness, whereas Al2O3/44%ZrO2 (4Y) was somewhat weakened in strength in despite of its highest fracture toughness.