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

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 degreesC, deformed by stationary creep in the range of strain rates similar to10(-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 (similar to0.2-0.4 mum) are homogeneously placed at alumina grain boundaries (similar to1-2 mum). (C) 2002 Published by Elsevier Science Ltd on behalf of Acta Materialia Inc.