Biaxial stretching of superplastic Y-TZP, Y-TZP/Al₂O₃, and Y-TZP/LAS glass composites in air atmosphere

The biaxial stretching behavior of superplastic Y-TZP (yttria-tetragonal zirconia polycrystals) ceramics and Y-TZP/Al₂O₃ composites in air atmosphere was investigated. Stretching deformation can be made within a limited range. Larger grain size of Y-TZP led to higher applied load needed to obtain the same amount of deformation. However, if some monoclinic phase was present in the materials, which was caused by the over-large grain sizes, defects would occur and thus make deformation easier. Microstructure study of the deformed specimen showed the occurrence of crack-like defects on the outside surface of the stretched disk specimen. Limited grain growth of single phase Y-TZP was obtained while Y-TZP grains in Y-TZP/Al₂O₃ composites grew extensively after stretching.