What are the changes in alumina ceramics under high temperature conditions

The changes in alumina ceramics under high temperature conditions include:

Creep. Because alumina ceramics are subjected to external forces at high temperatures, plastic deformation will slowly and continuously occur over time, a phenomenon we can call creep.

Graphitization and spheroidization. Due to the relatively low strength and mainly appearing in flakes of graphite, it can lead to a significant decrease in strength and an increase in brittleness of alumina ceramic materials, which is why we call it graphitization. At high temperatures, alumina ceramics contain a large amount of carbides inside, resulting in the formation of coarse-grained carbides, which are directly mixed with ferrite. The main reason is that carbides gradually transform from flakes to spheres, hence we call it spheroidization.