Cavity development during creep deformation in alumina with a bimodal grain size distribution

Abstract

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.