Ceramics superplasticity: Deformation mechanisms and microstructures

The superplasticity shall be generally achieved by grain refinement of various ceramics (ionic polycrystals and covalent polycrystals). This nature can be utilized for novel deformation processing in ceramic industy, for example, superplastic forming and superplastic forging. The superplasticity is a macroscopic phenomena that is very sensitive to slight difference in atomistic structure, and nature and chemical bonding of grain boundary. The mechanism of superplasticity is grain boundary sliding accommodated by matter transport through grain boundary. The models developed for superplasticity are classified by the structure of grain boundary. The experimental results on superplasticity of Zro2 and Si3N4 were reviewed and compared to the predictions from the theories.