The influence of sintering process on the microstructure of submicron alumina fabricated by gelcasting

Using ultra-fine alumina powders as raw materials, the submicron transparent alumina with relative density more than 99.9% was fabricated by gelcasting and then sintering-HIP process. It was found that only the samples with relative density more than 95% after presintering could obtain fully densification by post-HIP treatment. The final grain sizes increased after post-HIP treatment and were decided by either HIPing temperature or presintering temperature, depending on which one is higher. The maximal strength can reach about 650MPa when grain size is about 1 mu m.