Creep and creep-recovery behavior in silicon-carbide-particle-reinforced alumina

Flexure creep and creep-recovery behavior were investigated for monolithic Al2O3 and 10-vol%-SiC-particle-reinforced Al2O3-matrix composites in an air atmosphere at temperatures of 1160 degrees-1400 degrees C, Two types of Si C particles were used: one has an average size of 2.7 mu m and has an amoun t of SiO2 impurities per unit surface area that is one order of magnitude h igher than the other, which has an average size of 0.6 mu m. Compared to th e creep behavior of monolithic Al2O3, the strain rate of the composites wit h the 0.6 mu m SiC particles (denoted here as S-10) did not decrease; the c omposites with the 2.7 mu m SiC particles (denoted here as L-10) exhibited excellent creep resistance. This difference was related to the microstructu ral features acid the oxidation behavior of the composites: the Al2O3 grain s in S-10 were mainly equiaxed, only similar to 10% of the Al2O3 grains wer e elongated, and most of the SiC particles that resided at the grain bounda ries or at triple-grain junctions were oxidized during creep, whereas the A l2O3 grains in L-10 were mostly irregularly shaped and elongated and most o f the SiC particles were entrapped in the Al2O3 matrix: grains, which preve nted the oxidation of the SiC particles, These different microstructural fe atures were associated with different amounts of SiO2 impurity content per unit surface area on the SiC particle surfaces. In addition, the monolithic Al2O3 showed no anelastic recovery when the load was removed; however, the composites exhibited significant anelastic recovery, especially for L-10, This phenomenon was attributed to the elongated grain morphology.