Superplastic properties of alumina-zirconia composites

Superplastic deformation of two alumina-zirconia composites batches: the first with tetragonal ZrO2 stabilised with 3 mol.% Y2O3 and the second with ZrO2 stabilised with 2 mol.% Y2O3 (containing alumina volume fraction 10 - 86%) was studied. Grain sizes of two constituents were about 0.18-0.37 μm in the batch 1 and 0.36-0.14 μm in the batch 2. The composites were studied as a function of stress (20-130 MPa) and temperature (1451-1623 K) in compressive and bending tests. The strain rate was analysed in function of alumina volume fraction. It appeared that, the bigger than predicted by the rule of mixture strain rate decrease in function of alumina volume fraction is caused by improved creep resistance due to zirconium and yttrium ions doping of alumina grains. In zirconia grains modified interface-controlled Coble creep and simultaneously the intragranular dislocations motions contribute to the accommodation of grain boundary sliding (which is now thought to be main mechanism of superplastic behaviour). (author)