Microstructure control of ceramics by solidification processing

研究了差热分析方法的发展、Al2O3-Y2O3体系中共晶体系的选择、三元氧化物对共晶组织和耦合生长区的影响，为共晶陶瓷的凝固工艺发展提供了理论依据。本项目开发了一种光学差热分析方法，该方法在2500K以下使用。利用该装置，用成核温度决定了共晶体系（平衡共晶体系和亚稳共晶体系）的选择。冷却速率大于5K/s和/或熔体温度高于2373K会抑制YAG成核，因此选择亚稳共晶体系。在Al2O3-YAG体系中，三元氧化物的加入抑制了凝固界面的传质，导致共晶结构细化。共晶成分在较宽的生长速率范围内形成共晶结构，但由于多面生长，耦合生长仅在较窄的组成范围内发生

Development of difference thermal analysis method, selection of the eutectic systems in Al2O3-Y2O3 system, effect of the ternary oxide on the eutectic structure and the coupled growth zone were investigated to develop solidification processing for the eutectic ceramics. An optical differential thermal analysis method was developed in the project, which was used up to 2500K.By using this equipment, Selection of the eutectic systems (equilibrium and metastable eutectic systems) was determined by nucleation temperature. Cooling rates more than 5K/s and/or melt temperature above 2373K depress the YAG nucleation and consequently the metastable eutectic system was selected. Addition of ternary oxide in the Al2O3-YAG system caused finer eutectic structure, because the addition deceased mass transfer at solidifying interface.The eutectic structure was formed in the eutectic composition in a wide growth rate range, although the coupled growth occurred only in a narrow composition range due to the faceted growth