The Microstructure And Toughening-Strengthening Mechanism Of The Al₂O₃-matrix Composite Ceramics

Researches on Al2Oa-matrixed ceramics with perfect mechanical properties are most significant to modern machining -technology. The recent development of Al2O3-TiC composite ceramics was introduced.Particle-dispersed is a mostly-used method to fabricate ceramic composites. Many researches have showed that the mechanical properties of Al2O3-matrix ceramics in which Ti(C, N), TiC or TiN was dispersed could be improved a lot, which might be widely used in the field of machining. Al2O3-matrixed ceramics were fabricated by gas pressure sintering (GPS) and GPS with Post-HIP based on current techniques in this experiment.For Al2O3-TiCN composite ceramics, the densitification process was controlled by the mechanism of solid phase sintering.! while the process was controlled by the mechanism of liquid phase sintering for the system of Al2O3-TiC/ TiN. Pores and abnormal grain growth were existed in the Al2O3-TiC composite ceramics, which contribute to the unstable mechanical propertiesThe mechanical properties, especially the bending strength was improved a lot by the process of Post-HIP. The properties was tended to be centered. The grain boundary and grain edges were more faintness after post-HIP. And the grain boundary was strengthened at high temperature and ultra-pressure?So the ceramics was mainly transgranular-fractured, while the samples was mainly intergranular-fractured before processing of Post-HIP.The micromorpholgy and grain boundary microstructure of the material were studied with SEM and TEM and the grain boundary phase composition were analyzed with EDS and X-ray The mechanical properties, micromorpholgy microstructure of grain boundary and phase composition of Al2O3 composite ceramics were systematically studied , the effect of additives, the relationship between microstructure and mechanical strength, the sintering mechanism of the material and influence factors of the structure and properties of Al2O3 composite ceramics were discussedrespectively.The toughening mechanism of the Al2O3-matrix composite ceramics has been investigated. It indicated that the micro-crack-toughening was the main factor for Al2O3-T1CN composite ceramics. Then the Toughening-Strengthening Mechanism of Al2O3-TiN-ZrO2-MgO was theoretically discussed.These basic researches were of guidance for optimizing processing techniques, by which ceramic materials with perfect properties might be obtained.