Plasticity and Microcracking in Shock‐Loaded Alumina

Using a 110‐mm‐diameter compressed‐gas gun, we performed two types of experiments on alumina samples. The first involved plate impacts with wave profile measurements made with a VISAR velocity interferometer. The second type was plate‐impact recovery experiments. SEM, TEM, and X‐ray diffraction analysis showed that grain plasticity begins below the Hugoniot elastic limit (HEL), leading to a compaction of the material. This compaction is not accompanied by microcracking in pure alumina up to 2 × HEL. In the case of alumina with an intergranular glassy phase, the deformation of the sample is accompanied by a microcracking of the glass. However, the microcracks are not interconnected at a stress level equal to 2 × HEL for an alumina with about 10% glassy phase.