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Creep Resistance of the Directionally Solidified Ceramic Eutectic of Al2O3/c-ZrO2(Y2O3)

Published online by Cambridge University Press:  01 February 2011

Jin Yi ,
Ali S. Argon  and
Ali Sayir
Jin Yi
Affiliation:
Mechanical Engineering Department, Massachusetts Institute of Technology, Cambridge, MA, 02139, U.S.A.
Ali S. Argon
Affiliation:
Mechanical Engineering Department, Massachusetts Institute of Technology, Cambridge, MA, 02139, U.S.A.
Ali Sayir
Affiliation:
NASA - John Glenn Research Center, Cleveland, OH, 44135
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Abstract

The creep resistance of the directionally solidified ceramic eutectic of Al2O3/c-ZrO2(Y2O3) was studied in the temperature range of 1200–1520°C both experimentally and by mechanistic dislocation models. The creep of the eutectic in its growth direction exhibits an initial transient that is attributed to stress relaxation in the c-ZrO2(Y2O3) phase, but otherwise in steady state shows many of the same characteristics of creep in sapphire single crystals with c-axis orientation. The creep strain rate of the eutectic has stress exponents in the range of 4.5–5.0 and a temperature dependence suggesting a rate mechanism governed by oxygen ion diffusion in the Al2O3. A detailed dislocation model of the creep rate indicates that much of the nano-scale encapsulated c-ZrO2(Y2O3) is too small to deform by creep so that the major contribution to the recorded creep strain is derived from the diffusion-controlled climb of pyramidal edge dislocations in the Al2O3 phase. The evidence suggests that the climbing dislocations in Al2O3 must repeatly circumvent the c-ZrO2(Y2O3) domains acting as dispersoids resulting in the stress exponents larger than 3. The creep model is in very good agreement with the experiments.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 791: Symposium Q – Mechanical Properties of Nanostructured Materials and Nanocomposites , 2003 , Q7.12
Copyright
Copyright © Materials Research Society 2004

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