SUPERPLASTIC GAS-PRESSURE DEFORMATION OF YTZ SHEET

The superplastic deformation behavior of fine-grained, yttria-stabiliz ed tetragonal zirconia under conditions of biaxial gas-pressure deform ation is described. Sheet specimens were deformed into hemispherical c aps at temperatures ranging from 1450-degrees to 1600-degrees-C and at imposed gas pressures ranging from 345 to 2760 kPa. For the forming c onditions examined, hemispherical caps were formed at times ranging fr om 2 to 476 min. A gas-pressure-forming apparatus used to conduct the experiments is described and a mechanical analysis of the deformation process is presented. Also discussed is the role of grain growth and t he relationship between data obtained in uniaxial testing and the beha vior observed during the biaxial deformation experiments of this study . A comparison is made between the observed thickness distribution in the hemispherical caps with predictions from an analytical model.