LOW-TEMPERATURE SUPERPLASTIC FLOW OF YTTRIA-STABILIZED TETRAGONAL ZIRCONIA POLYCRYSTALS

Very fine-grained (0.2 mum), dense Y-TZP ceramics have been produced by free sintering at 1150-degrees-C. The superplastic deformation of these materials is studied in compression at low temperatures (1100-1300-degrees-C). A significant enhancement in initial strain rates was observed compared to a coarser-grained (0.4 mum) commercially available material (Tosoh, Japan). Doping with small amounts of Fe2O3 led to a further enhancement of strain rate. Deformation occurred via interface reaction controlled grain boundary sliding. Prior to deformation a continuous glassy silicate film was observed at the grain boundaries. The applicability of interface reaction controlled solution-precipitation creep models is discussed. The absence of a steady-state during deformation at low stresses is attributed to dewetting of the silicate film.