Superplastic behavior of zirconia-reinforced alumina nanocomposites from powder alcoxide mixtures Original Research Article

Here we report the synthesis, microstructure and superplastic creep behavior of alumina-based composites reinforced with 5–20 wt% ZrO2, prepared from high-purity alumina powders and zirconium alcoxide precursor mixtures. The composites reached 100% true strain at 1350 °C, deformed by stationary creep in the range of strain rates ~10−7 to 10−4 s−1. The microstructure remained stable during creep; no evidence of grain growth, grain boundary opening or cracking were observed in deformed samples. We conclude from the analysis of creep parameters that creep takes place mainly by interface-reaction-accommodated grain boundary sliding, and that the mobility of alumina grain boundaries controls the creep rate. The observed behavior is explained by the role of alumina–zirconia interphases, stronger and with a faster relaxation kinetics than alumina interfaces, to achieve an effective grain boundary pinning. Zirconia particles (~0.2–0.4 μm) are homogeneously placed at alumina grain boundaries (~1–2 μm).