UNIAXIAL-STRESS BEHAVIOR OF Y-TZP

Uniaxial stress behaviour of yttria-tetragonal zirconia polycrystal (Y -TZP) was investigated using a novel split Hopkinson pressure bar tech nique. The Y-TZP specimens were loaded by a single compressive pulse o f predetermined shape and duration. The stress-strain response of the material revealed a linear elastic regime followed by an inelastic reg ime during which tetragonal to monoclinic transformation occurs. After the transformation was complete, the stress-strain behaviour was foun d to be elastic with a slope similar to that of the untransformed mate rial. This behaviour suggests that the modulus of the transformed mono clinic zirconia is essentially the same as that of the untransformed t etragonal zirconia, and microcracking during transformation does not s ignificantly affect the subsequent uniaxial stress-strain relation in Y-TZP. Ultrasonic measurements before and after the experiments, and m icroscopic observations on transformed zirconia specimens also support this conclusion, the latter revealing a very small number of nanometr e-size cracks where martensitic laths in partially transformed grains interface with grain boundaries.