EFFECT OF GRAIN SIZE ON SUPERPLASTIC DEFORMATION AND CAVITY FORMATION IN 3 MOL YTTRIA-STABILIZED ZIRCONIA POLYCRSTAL

摘要

Most materials tend to cavitate during superplastic deformation and cavitation proceeds generally by three stages, namely nucleation, growth and coalescence of voids under the effect of flow stress. Cavities either nucleate or develop from pre-existing defects and their growth, coalescence and interlinkage leads to premature failure. The factors influencing cavity nucleation during superplastic flow include those relating to microstructure such as grain boundary particles, grain size, phases and those associated with deformation conditions, such as strain, strain rate, stress and temperature. In the present study, the effect of grain size on superplastic deformation and cavity formation in 3 mol% yttria-stabilized zirconia polycrstal has been examined. Also the distribution of cavity size has been quantitatively determined as a function of grain size. The results demonstrated that the amount of cavitation increases with increasing grain size.