High temperature plasticity in yttria stabilised tetragonal zirconia polycrystals (Y-TZP)

Abstract

The literature data on the superplastic deformation of high purity yttria stabilised tetragonal zirconia polycrystals is reviewed in detail. It is shown that, based on the existence of a threshold stress, the single mechanism of grain boundary sliding (GBS) accommodated by diffusional processes can explain the superplasticity of these materials over all the ranges of temperature, stress, grain size, and surrounding atmosphere that have been studied. The origin of the threshold stress and its quantitative dependence on temperature and grain size is explained in terms of the segregation of yttrium atoms at the grain boundaries. A new model for GBS accommodated by lattice or grain-boundary diffusion is presented which can explain the transition of the stress exponent from 2 to 1.

Comparative study on high temperature mechanical behavior in 3YTZP containing SWCNTs or MWCNTs

“…Monolithic 3YTZP shows a stress exponent n=1.7 and n=2.1 at 1100 and 1200 ºC respectively. These values are close to 2, in agreement with results previously reported [22][23][24], where grain boundary sliding GBS accommodated by cationic diffusion throughout the lattice was recognized as the high temperature deformation mechanism. In case of composites, the stress exponent values are slightly higher but between 1.7 and 2.5.…”

Superplasticity and superplastic-like flow in cubic zirconia with silica

“…For 8Y-CSZ without silica [63], the activation energy was measured as *510 kJ mol -1 where this is close to the activation energy of *600 kJ mol -1 obtained in the present experiments for 8Y-CSZ with silica. There are no reliable data for the activation energy for diffusion along the grain boundaries in the yttria-zirconia system [65] but, based on diffusion data reported for a tetragonal ceria-zirconia-hafnia solid solution, it appears that these results are reasonably consistent with diffusion of the Zr 4? ions along the grain boundaries [66].…”

Deformation behavior of nanocrystalline titania particles accessed by complementary in situ electron microscopy techniques

“…5,6 At these temperatures, thermally activated and enhanced processes such as grain boundary sliding, dislocation slip and climb, as well as diffusion-mediated creep mechanisms can contribute to large deformations. 5,6 At these temperatures, thermally activated and enhanced processes such as grain boundary sliding, dislocation slip and climb, as well as diffusion-mediated creep mechanisms can contribute to large deformations.…”