Superplastic deformation mechanisms during creep of alumina-zirconia composites

The high temperature creep of three alumina-zirconia composites (alumina volume fraction: 20%, 50% and 80%) and of the end-constituents (Y-PSZ and alumina) has been studied as a function of stress (4-200 MPa), temperature (275-1400 degrees C) and grain size (0.4-2 mu m). The deformation of the end-constituents results from two serial mechanisms (interface reaction and diffusion, preponderant at low or high stress, respectively). The shape of the creep rate-stress curves of composites was similar to that of the end-constituents, suggesting similar deformation mechanisms. The influence of the alumina volume content on the creep rate of the composites has been analysed by various models. The model that accounts best for the composite behaviour is a ''three-phase'' model. The influence of grain size shows that the creep rare accommodation is connected with alumina-zirconia interfaces. (C) 1997 Acta Metallurgica Inc.