ABSTRACT
The phenomenon of superplasticity has been observed in several single and dual phase ceramics. Typically, the dependence of creep rate ( https://www.w3.org/1998/Math/MathML"> ε ˙ https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003421290/07e4de97-c68f-4ca1-95b4-28d8b410031d/content/eq357.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> ) on stress (σ) is characterized by https://www.w3.org/1998/Math/MathML"> ε ˙ α σ n https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003421290/07e4de97-c68f-4ca1-95b4-28d8b410031d/content/eq358.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> , where n is the stress exponent. Previous studies on superplastic ceramics have reported values of n ranging from 1 to 3 for nominally identical materials, and the discrepancy has been attributed partly to differences in the content of minor impurities. This paper describes the results of a detailed creep study on fine-grained superplastic zirconia. The deformation behavior was characterized under constant stress in uniaxial compression over the temperature range of 1600 to 1750 K. Two distinct creep behaviors were observed: at higher stresses n~2, whereas at lower stresses n~3. These results are compared to the available theoretical creep models.
