Superplasticity in Ceramics

It is clearly demonstrated that the superplasticity is one of the common properties of fine-grained ceramics at elevated temperatures. The paper reviewed the major features of superplasticity in ceramics, the deformation characteristics and mechanism of yttria-stabilized tetragonal zirconia polycrystals(Y-TZP), a typical superplastic ceramic. The reason for the difference in region I between high-purity and low-purity Y-TZP was explained, then the effects of impurities on the apparent stress exponent were found out. The rate controlling mechanism in superplasticity was also analyzed from the point of activation energy. The superplastic characteristics of SisN4 covalent ceramics enhanced by intergranular glass phase was studied, hence the role of the intergranular glass phase in superplasticity was defined. The superplastic behavior of other ceramic materials, including AlaOs, aluminium based composites, covalent ceramic materials and nano-structured ceramics were also summarized.