Study On The Preparation And Microstructure Of Al₂O₃/SiC Nano-composites

Alumina (Al₂O₃) was a widely used ceramic due to its refractoriness, wear resistance and chemical stability. However, the brittleness of Al₂O₃ limited its potential applications. In this paper, nano-SiC particle toughened Al₂O₃ ceramics were studied. The nano-composites possess higher mechanical properties than monolith alumina.The dispersing of nano-particle was researched. We studied the suitable dispersing method and processing for the Al₂O₃/SiC system. Obtained best parameters and prepared the powders those have excellent properties.The abnormal grain growth of Al₂O₃ often occurs during sintering of commercial purity Al₂O₃. By means of controlling sintering process and contents of SiC to produce tailored microstructure, the optimum properties were obtained.The sintering mechanism of Al₂O₃/SiC ceramic nanocomposite was researched. We divided the sintering process into three parts. The priority of densification occurred in aggregated nano-particles. Dispersion of mixed original powders and the SiC content in composites was important.The formation of intragranular microstructure depended on driving force of interface and movement velocity of inclusion and matrix grain bounding. Higher grain surface energy and lower curvature radius of dispersoids contribute to more intragranular particles.In Al₂O₃/SiC nano-composites, the SiC particles were uniformly dispersed in Al₂O₃ matrix. Part of nano-SiC, is embedded in Al₂O₃ grains, and another nano-SiC particles is existed at Al₂O₃ grain boundaries. Nano-composites with intragranular microstructure was successfully prepared. Al₂O₃/SiC nano-composites possessed favorable mechanical properties. The maximum strength and toughness are 668.02Mpa and 4.9MPa·m^1/2, were significantly improved compared to monolith alumina.The grain boundaries of Al₂O₃ were strengthened by SiC. Intragranular nano- SiC changed the fracture mode of Al₂O₃ from intergranular fracture to intragranular fracture. Various strengthen and toughen mechanism acted on Al₂O₃/SiC nano-composites. That was the intragranular SiC makes the Al₂O₃ grains into nano size,refined microstructural strengthen mechanism of SiC and deflection of crack.