Deformation and failure of alumina under high strain rate compressive loading

For development of structural ceramics e.g., alumina for high strain rate resistant applications, it is extremely important to understand the issues involved in compressive microfracture and the role of compressive microfracture in the global failure process at high strain rates. Thus the present work reports compressive strength of a dense (e.g., ρ ~97.2% ρth) 5 μm grain size alumina exposed to high strain rate (e.g., 0.9×103 s−1) loading in SHPB experiments. Concomitant utilization of high-speed videography has been exploited to study in-situ the details of the dynamic fragmentation process. The maximum compressive strength is measured to be ~3 GPa. Post-mortem examination of the recovered alumina fragments has been performed by FESEM and TEM. Apart from conventional global brittle fracture, the results show the grain localized microcleavages, intragranular microcracking, plasticity, dislocations as well as formation of subgrain structure to occur in alumina. Based on these experimental results the reasons of compressive microfracture and its probable role in the global failure process of alumina ceramic are discussed.