Dynamic plasticity and failure of high-purity alumina under shock loading

High-resolution electron microscopic study of high-purity AD995 alumina, softly recovered from conventional shock loading experiments, is discussed. The transition point from elastic to inelastic response prior to failure during shock loading, known as Hugoniot elastic limit (HEL), was used to estimate the important parameters in the characterization of dynamic mechanical properties of ceramics. The alumina samples were recovered intact, but it showed a visual evidence of extensive microscopic cracks. The deformation and failure mechanism operating in shock-loaded alumina were investigated using scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The experimental observation of the deformation behavior from dislocation activity in the vicinity of grain boundaries to deformation twinning, provides an evidence of micromechanism responsible for shock-induced global plastic deformation in AD995 alumina.