Microstructure and micro-mechanical properties of Y-TZP and Y-TZP/Al₂O₃ composite after superplastic deformation

The microstructure and micro-mechanical properties of superplastically deformed Y-TZP ceramics and Y-TZP/Al₂O₃ composites were investigated. The grain growth on average of the pure Y-TZP ceramics during deformation at the temperature 100°C below the sintering temperature was very limited, while extensive growth of Y-TZP grains in Y-TZP/alumina composites were found under the same condition. The segregation of Y³⁺ in single phase Y-TZP and the glass phase present at triple points in the composites was believed to be responsible for the different grain growth behavior. The change of mechanical properties of the materials were found to mainly relate to the microstructural change of the materials during deformation. In the case of single phase Y-TZP ceramics, both Vicker's hardness and indentation toughness do not apparently change by deformation, but the indentation toughness of the Y-TZP/alumina composites decreased noticeably due to the extensive grain growth of Y-TZP and thereafter the occurrence of monoclinic zirconia phase.