Abstract: The compressive plastic deformation of superplastic 3 mol% yttria-stabilized zirconia polycrystalswith different grain sizes was studied by both constant cross head speed and constant load tests incompression in air. The superplastic-like phenomenon in 3Y-TZP was exhibited. The grain shape remainedequiaxed and the grains were dislocation-free after deformation. It indicated that the deformationmechanism was grain boundary sliding accommodated by diffusion. The flow stress decreased markedly with theincrease of the strain rate and grain size and with the decrease of the temperature. The stress exponent and activation energy for creep decreased from 3.2 to 1.4 and from 580jK/mol to 500kJ/mol with the increment of the grain size from 0.30μm to 1.33μm, respectively. That the change in the stress exponent and activation energy implied the change in deformation mechanism with the grain size. Cavitation occurred at triple junctions in the materials with coarser grain sizes during deformation at high strain rates and a part of the cavities developed along grain boundaries and linked as crack-like cavities.

Key words: tetragonal zirconia polycrystals, deformation, superplasticity, creep, cavitation