Tensile failure in a superplastic alumina

Abstract

Abstract Tensile failure in superplastic alumina shows a close similarity to ductile failure in metallic materials containing microvoids or hard inclusions. Microcracking, which appears as strain exceeding ∼ 90% of the failure strain and leading to macroscopic cracking for final failure, is not caused by the propagation of the largest preexistent defects, but by extensive cavity coalescence. Such coalescence is found to occur as the thickness of the intervoid matrix decreases to a certain level due to an increase in the number and size of cavities. The data also show that there is no explicit critical grain size for the onset of microcracking, although microcracking and failure tend to occur at smaller strains as the initial grain size increases.