Microstructure Evolution of Melt-grown Al₂O₃/ZrO₂/YAG Eutectic Ceramic by High Temperature Fused Method

Abstract

As ultra-high-temperature structural materials, the mechanical properties of eutectic oxide ceramics are closely related with microstructure characteristics. Melt-grown Al2O3/ZrO2/YAG eutectic ceramic was prepared by high temperature fused method. Effect of melt temperature and crystal seed on solidification microstructure evolution was investigated, the structure evolution mechanism was discussed using the classical nucleation mechanism and Jack-hunt mode. Experiment results show the phase composition of solidified samples changes from α-Al2O3/c-ZrO2/YAG to α-Al2O3/c-ZrO2/YAP as the melt temperature increases from 1750℃ to 2000℃. And the solidification microstructure evolves as follows:non-eutectic ceramic Al2O3/ZrO2/YAG, irregular eutectic ceramic Al2O3/ZrO2/YAG, nano-scale regular fibrous pattern eutectic Al2O3/ZrO2/YAG, and complex coarse metastable composite ceramic Al2O3/ZrO2/YAP. Analysis shows that microstructure evolution is resulted from heterogeneous passivation with elevating temperature followed by variations of nucleation undercooling and solidification path. Therefore, choosing reasonable melt temperature and crystal seed are the key rules to control the microstructure of Al2O3/ZrO2/YAG eutectic ceramic.

Keywords

• high temperature fused method
• eutectic ceramic
• undercooling
• solidification microstructure
• passivation