Ultra-high temperature compressive creep behavior of an in-situ Al2O3 single-crystal/YAG eutectic composite

Compressive creep tests were conducted for an in-situ single-crystal alumina/yttrium aluminum garnet [Al2O3/Y3Al5O12(YAG)] eutectic composite for a specimen with a compressive axis with 0 or 90degrees to the solidified direction at temperatures between 1723 and 1923 K under stress ranges of 140-450 MPa in air environments. The single-crystal Al2O3/YAG eutectic exhibited a stress exponent of 5.4-10, indicative of compressive creep behavior characterized by a dislocation mechanism. Activation energies for creep deformation were 810-1024 kJ/mol, close to that for 42degrees from c-axis single-crystal Al2O3 or single-crystal YAG, in agreement with that of self-diffusion for c-axis single-crystal Al2O3. The 0degrees specimen exhibited a slight decrease in creep rate by about half for a 90degrees specimen corresponding to results from crystal anisotropy in single-crystal Al2O3. The Larson-Miller method provided an effective means of comparing creep resistance of oxides on the basis of results obtained under different stresses and temperatures. (C) 2003 Elsevier Ltd. All rights reserved.