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摘要
Al2O3-Si3N4 composites ceramic tool materials with Y2O3 as sintering additive were fabricated by the hot pressing process at 1450 degrees C for 30 min under 32 MPa in vacuum. Different mass fractions of Si3N4 as reinforcements were employed. The mechanical properties, microstructure, strengthening and toughening mechanisms of the composites were investigated. The content of Si3N4 had significant effect on the mechanical properties and microstructure of the composites. Al2O3-25 wt% Si3N4-1 wt% Y2O3 had the optimum comprehensive mechanical properties with flexural strength, fracture toughness, Vickers hardness and relative density of 768.7 +/- 63.9 MPa, 6.8 +/- 0.4 MPa m(1/2), 19.6 +/- 0.4 GPa and 99.6 +/- 0.2% respectively. A core shell structure with Si3N4 as core and Al2O3 as shell was firstly formed in the composite. The core-shell structure was generated through a rapid dissolution transport precipitation process. Elongated beta-Si3N4 grains with a diameter of 0.3-0.5 mu m and aspect ratio of 5 were in-situ synthesized. The improved mechanical properties were attributed to the strengthening and toughening mechanisms including the mixed fracture mode of intergranular and transgranular fracture, the crack deflection, the high grain boundary strength, the pinning and bridging effects of the core-shell structure and the elongated grains.
- 出版日期2015-12
- 单位山东大学
