Low-temperature deformation behavior of nanocrystalline 5 mol% yttria stabilized zirconia under tensile stresses

Nanocrystalline 5 mol% yttria stabilized zirconia ceramics (n-5Y-TZP) with relative densities of about 80 % and grain sizes between 30 and 60 nm were deformed plastically in tension at 1050 degrees C (< 0.4 T-m). Total strains exceeding 0.2 and strain rates as high as 10(-5) s(-1) without failure were observed. Porosity was not found to be critical for the ability to deform without cracking. A preliminary estimate of the grain size exponent in the constitutive equation for superplastic flow yields a value of 1.3. Furthermore, the stress exponent is determined to be 2.7 and related to a deformation model based on grain boundary sliding as the rate controlling process. (C) 1998 Acta Metallurgica Inc.