Phase Transformation and Domain Switching Behaviors during Superplastic Deformation in 3Y-TZP

Abstract

Test pieces of a tetragonal zirconia polycrystal containing 3mol% yttria were deformed in tension under superplastic conditions in air to pre-determined nominal strains ranging from 0.0 to 200%. The X-ray diffraction experiments were conducted on surface regions of gauge sections of the deformed test pieces to investigate phase transformation and domain switching behaviors that might occur during the superplastic deformation. The measured X-ray patterns were analyzed using a Rietveld refinement method. As a result: (i) Reflections from monoclinic (m) phase were not observed in the X-ray patterns, indicating that tetragonal (t) to m phase transformation might not occur during superplastic deformation under the above condition. Meanwhile, the fraction of cubic (c) phase seemed to decrease with increasing strain. (ii) Traces of ferroelastic domain switching were observed in the X-ray patterns of the deformed specimens. The switching amount was found to depend on flow stress and deformation amount. The tetragonal axis ratio (c/a) along the scattering vector used in this study was found to decrease with increasing the switching amount.