Cavity Development During Creep Deformation in Alumina with a Bimodal Grain Size Distribution

An alumina sample, codoped with equimolar proportions of magnesia and zirconia, exhibited a bimodal grain size distribution after hot‐pressing. Flexural creep experiments were performed on this material at temperatures of 1673 and 1773 K in air. Inspection of the deformed specimens revealed extensive creep cavitation, with cavities developing preferentially in the coarse‐grained regions. The nucleation, growth, and interlinkage of the cavities led to the formation of cracks. Crack growth occurred in the coarse‐grained regions by the linkage of cavities with the crack tip. However, several cracks were observed to terminate after extending up to a fine‐grained region of a specimen. A model has been developed to rationalize the observation that preferential cavitation occurs in the coarse‐grained regions of a specimen undergoing creep deformation.