Superplastic Forming of Ceramics

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The results obtained are summarized as follows,(1) The high-temperature deformability in TZP is improved by an addition of small amount of grain boundary glass phase. The addition of 5 wt% lithium-aluminosilicate glass results in about 200ﾟC decrease of superplastically deformed temperature. TZP containing this glass deforms superplastically at 1100ﾟC.(2) The marked grain growth and cavitation during high-temperature deformation retards the tensile ductility of high-purity Al_2O_3. The MgO addition effectively suppresses the grain growth of Al_2O_3 and consequently improves the ductility. The maximum elongation obtained is 70% at 1400ﾟC.(3) The high-temperature flow stress in Al_2O_3-ZrO_2 depends markedly on zirconia content. A sharp peak value is obtained in Al_2O_3-2wt%ZrO_2. The composition dependence of flow stress can qualitatively be explained by assuming that the grain boundary sliding is much difficult along Al_2O_3/ZrO_2 boundary than other boundaries.