YAG引入方式对碳化硅陶瓷烧结特性、力学性能及结构的影响

Effects of adding methods of YAG on sintering behaviour,mechanical properties and microstructure of SiC ceramic

采用溶胶凝胶法和机械共混法分别引入烧结助剂YAG(Y3Al5O12)和Al2O3+Y2O3 制备复合粉体, 经过无压液相烧结制备碳化硅陶瓷材料, 分析了烧结助剂引入方式对碳化硅陶瓷烧结、性能及结构的影响机制。研究结果表明, 在1 950℃烧结45 min时, 机械共混法制备的复合粉体可以获得较好的烧结性能, 陶瓷具有较好的力学性能和显微结构, 而溶胶凝胶法制备的复合粉体则存在过烧。经烧结工艺优化, 溶胶凝胶法制备的复合粉体在1 860℃烧结1 h后, 陶瓷可以获得更优的烧结性能、力学性能及更理想的显微结构。复合粉体中YAG相的提前形成及均匀分布促进复合粉体的快速致密, 降低烧结温度, 改善陶瓷的力学性能及显微结构。细晶、裂纹偏转和晶粒桥联是碳化硅陶瓷的主要增韧机制。

SiC composite powders were respectively synthesized by sol-gel method and mechanical mixing method, and were pressureless liquid-phase sintered to prepare silicon carbide ceramic. The effects of adding methods on the sintering behaviour, mechanical properties and microstructure of silicon carbide ceramic were analyzed. The results show that at the sintering temperature of 1950℃, silicon carbide ceramic, with SiC/(Al_2O_3+Y_2O_3) composite powder by mechanical mixing method, possesses higher sintering properties, higher mechanical properties and more ideal microstructure than those with SiC/YAG composite powder by sol-gel method, and there exists over-sintering phenomenon in the SiC/YAG composite powder. After optimizing the process, silicon carbide ceramic, sintered at (1860℃) with SiC/YAG composite powder by sol-gel method, can obtain excellent sintering and mechanical properties and perfect microstructure. Formation ahead of sintering and uniform distribution of YAG phase in composite powder can accelerate the densification, decrease sintering temperature and improve mechanical properties and microstructure of silicon carbide ceramic. The fine grains, crack deflexion and grain-bridging are main toughening mechanisms of silicon carbide ceramic.