单相籽晶诱导定向凝固Al2O3/YAG两相共晶陶瓷晶体学取向的研究

Directionally solidified Al2O3/Y3Al5O12 (YAG) eutectic ceramic has recently been considered as a new generation of turbine material because of its high melting point, low density, superior oxidation and creep resistance and excellent high temperature strength. In order to improve its properties such as the fracture toughness and strength, the present project was designed to prepare Al2O3/YAG eutectic ceramic with single-phase seed technique. Different crystallography and interfacial relationship of Al2O3/YAG eutectic ceramic are expected to be prepared by single crystal Al2O3 and single crystal YAG with different orientations. The present project focuses on the microstructure, crystallography evolution and typical interfacial structure of the Al2O3/YAG eutectic ceramic at different growth stages. The hardness, toughness and flexural strength of the as-prepared Al2O3/YAG eutectic ceramics will also be investigated. Together with the model building of the crystallographic relationship, calculation of the planar disregistry and ionic charge balance principle, the project will explore the effect mechanism of the interfacial energy on the crystallography of the Al2O3/YAG eutectic ceramic. The project will finally put forward the basis and principle for crystallography and interfacial relationship design of the Al2O3/YAG eutectic ceramic, and build the crystallography-property relationship. This study might cast light for design of high-performance Al2O3/YAG eutectic ceramics.

定向凝固Al2O3/Y3Al5O12(YAG)共晶陶瓷以其高熔点、低密度、优异的抗氧化、抗蠕变性能和高温强度被认为是新一代涡轮发动机热端用材料。为进一步提高其断裂韧性、强度等性能，本项目提出采用单相籽晶诱导Al2O3/YAG两相共晶陶瓷取向生长的新方法，分别采用不同取向的单晶Al2O3和单晶YAG作为籽晶设计Al2O3/YAG两相共晶陶瓷的晶体学取向和相界面结构。研究Al2O3/YAG共晶陶瓷不同生长距离截面处组织结构、晶体学取向和典型相界面结构，测定不同取向Al2O3/YAG共晶陶瓷的硬度、断裂韧性和弯曲强度等性能。结合平行相界面内晶格匹配模型的建立、平面错配度计算和电荷平衡原则，揭示相界面能对Al2O3/YAG共晶陶瓷晶体学取向的影响机理，提出Al2O3/YAG共晶陶瓷取向和相界面关系设计原则，并建立晶体学取向-性能关系，为设计具有更高性能的Al2O3/YAG共晶陶瓷提供新思路。

本项目针对研制新一代具有更高承温能力叶片材料的需求，力求设计和制备具有更高断裂韧性和更高弯曲强度的定向凝固Al2O3/YAG共晶陶瓷，其难点在于采用单相籽晶是否能诱导成功双相共晶陶瓷的取向。重点采用r-[1-102]、m-[10-10]和a-[11-20]单晶Al2O3籽晶诱导制备了双相Al2O3/YAG共晶陶瓷；表征了凝固起始阶段和顶端位置的晶体学取向关系，建立了平行晶面的晶格匹配模型并计算了平面晶格错配度，分析双相Al2O3/YAG共晶陶瓷中的相界面对于晶体学取向关系的影响机制；完成诱导制备的双相Al2O3/YAG共晶陶瓷弯曲强度、硬度及断裂韧性的测试等研究内容，建立晶体学取向-性能之间关系。