High-temperature deformation behaviour of TiO2-doped 8 mol.% Y2O3-stabilized ZrO2 (8Y-CSZ) under tension and compression

The effect of TiO2 addition on the phase stability of 8 mol.% yttria-stabilized cubic zirconia (8Y-CSZ) was investigated. XRD results showed that when the TiO2 amount was less than 5 wt.%, the specimens were entirely single cubic phase; further addition of TiO2 (5 wt.% or more) destabilized cubic zirconia phase and caused the formation of tetragonal phase. The amount of tetragonal phase increased with increasing TiO2 content in the 8Y-CSZ matrix. The high-temperature deformation behavior of TiO2-doped 8Y-CSZ was also studied under both tension and compression. The stress exponent and the activation energy values for 10 wt.% TiO2-doped 8Y-CSZ were found to be 1 and 340 kJ/mol, respectively, using strain rate data from compression tests. The microstructure after and prior deformation was investigated using TEM. The grain shape remained equiaxed after extensive deformation but a high degree of residual stress developed. Under tension the addition of TiO2 vastly decreased the flow stress for 8Y-CSZ and increased elongation to failure. The maximum elongation for 10 wt.% TiO2-doped 8Y-CSZ was 203% at 1400 °C and at an initial strain rate of 1.3 × 10−4 s−1 with a flow stress of 8 MPa, indicating the superplastic nature of this material.