A three phase ceramic composite of 8 mol% Y2O3 stabilized ZrO2 (YSZ), SiO2, and Al2O3 was evaluated for potential high temperature superplasticity. The amorphous SiO2 content was 5 wt.%, and increasing additions of Al2O3 were made. The effect of varying the Y2O3 stabilizer concentration in ZrO2 was also studied. Samples sintered at 1200 °C contained only YSZ, Al2O3, and amorphous SiO2, but ZrSiO4 formed in the samples above 1300 °C. Mullite (3Al2O3 · 2SiO2) was not detected in any samples. Specimens of 1 wt.% Al2O3–YSZ/SiO2 had an anomalously high deformation rate of ∼2 × 10−4 s−1 at 1200 °C when compared to YSZ/SiO2 without Al2O3 (∼4 × 10-5 s−1). Higher amounts of Al2O3 additions decreased the strain rate. Extensive deformation of Al2O3 doped YSZ/SiO2 at 1200 °C induced the formation of ZrSiO4 due to enhanced reaction rates. This distributed, yet locally interconnected, zircon phase rapidly eroded the strain rate after ∼60% deformation.
Zircon Al2O3 Y2O3 High Temperature Deformation Initial Strain Rate
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This work was supported by the National Science Foundation under Grant No. DMR-0207197.