Transient p, or Andrade, creep occurs when magnesiapartially-stabilized zirconia is loaded in tension at room temperature. The equation relating the longitudinal or tensile creep strain, E; to the tensile stress, u, and to the time, t, has been determined to be E; = Au'"t" in which the constants A, m, and n depend on the phase content of the zirconia. Observations are reported of the tetragonal-tomonoclinic and tetragonal-to-orthorhombic phase transformations which occur during creep: there is also a progressive development of microcracking. It is shown that a combination of these phenomena can account for the observed creep behavior.
The measured plastic deformation of Mg-PSZ under stress contains contributions from both transformation and microcracking. A method is described to separate the contributions from transformation and microcracking for samples deformed in uniaxial tension. Such a separation enables the ratio of the longitudinal to transverse strains arising from the transformation to be estimated. The results are compared to the predictions of the shear-dilatation model of Chen and Reyes-Morel. Serious discrepancies are found between the experimental results and the predictions of the model and the possible reason for this is discussed.
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