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Atmospheric Effects on Compressive Creep of SiC‐Whisker‐Reinforced Alumina
Author(s) -
Lipetzky Pete,
Nutt Steven R.,
Koester David A.,
Davis Robert F.
Publication year - 1991
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1991.tb04092.x
Subject(s) - creep , whisker , materials science , composite material , cavitation , composite number , deformation (meteorology) , grain boundary , diffusion , diffusion creep , stress (linguistics) , phase (matter) , compression (physics) , thermodynamics , microstructure , chemistry , physics , philosophy , organic chemistry , linguistics
A SiC‐whisker‐reinforced alumina composite was crept in compression at 1200° to 1400°C in an air ambient and in nitrogen. The data were described by a power‐law‐type constitutive relation. The measured value of the stress exponent was n = 1 at 1200°C and n = 3 at 1300° and 1400°C in both ambients. TEM observations were correlated with the measured creep response to determine active deformation mechanisms. Values of n = 1 were associated with diffusional creep and unaccommodated grain‐boundary sliding, while values of n = 3 were associated with increased microstructural damage in the form of cavities. Experiments conducted in circulated air resulted in higher creep rates than comparable experiments in nitrogen. The accelerated creep rates were caused by the thermal oxidation of SiC and the resultant formation of a vitreous phase along composite interfaces. The glassy phase facilitated cavitation, weakened interfaces, and enhanced boundary diffusion.