Compressive deformation properties and microstructures in the superplastic Y-TZP

Abstract

The superplastic deformation properties of 3mol% Y2O3-stabilized tetragonal ZrO2 polycrystals (Y-TZP) were studied by uniaxial compression tests in air at temperatures up to 1500°C with strain rates ranging from 10-3 to 10-5s-1. The effect of microstructure on the superplasticity was also examined, Fine-grained Y-TZP with an average grain size of 0.3-0.4μm was deformed to the true strain of more than -1.5. The macroscopic strain rate (e) in superplasticity was expressed phenomenologically by the following equation, e=2×10-5exp(-380000/RT)σ2.1/d1.8, where T, σ, and d are temperature, stress, and grain size, respectively, and R is the gas constant. Although the microstructure of the deformed specimen showed slight grain growth and slight anisotropic deformation of each grain, the large strain was mainly caused by the grain boundary sliding. The cavitation was not observed in the compressed specimens. ZrO2 particles maintained tetragonal or cubic phase after the superplastic deformation. The deformation properties and the observed microstructure in the superplasticity of Y-TZP were explained by the Gifkins's model.