MICROSTRUCTURE AND MICROMECHANICAL 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 deforma tion at the temperature 100 degrees C below the sintering temperature was very limited, while extensive growth of Y-TZP grains in Y-TZP/alum ina composites were found under the same condition. The segregation of Y3+ in single phase Y-TZP and the glass phase present at triple point s in the composites was believed to be responsible for the different g rain growth behavior. The change of mechanical properties of the mater ials were found to mainly relate to the microstructural change of the materials during deformation. In the case of single phase Y-TZP cerami cs, both Vicker's hardness and indentation toughness do not apparently change by deformation, but the indentation toughness of the Y-TZP/alu mina composites decreased noticeably due to the extensive grain growth of Y-TZP and thereafter the occurrence of monoclinic zirconia phase. (C) 1998 Acta Metallurgica Inc.