Plastic deformation of ceramics via quasistatic and high strain rate nanoindentation

Abstract Nanoindentation testing conducted at low and high strain rates holds great promise as a technique for measuring strain rate sensitivity and exploring the plastic deformation mechanisms of ceramic materials that cannot be studied in standard tension tests because of their inherent brittleness. In this study, we employ a high strain rate nanoindentation testing system, combined with transmission electron microscopy, to investigate the intrinsic mechanisms of plastic deformation in two ceramic materials. The investigations encompass a wide range of indentation strain rates, spanning from a low of 10 −2 s −1 to a high of 10 4 s −1 , using single crystal MgO (111) and Al 2 O 3 (0001) as model materials. The results reveal that MgO exhibits a clear dependence of hardness on strain rate, while for sapphire, the influence of strain rate on hardness is negligible. The mechanisms underlying the distinct strain‐rate responses of the two materials were revealed through microstructural investigations beneath the indent. Overall, the results demonstrate the promise that nanoindentation testing techniques have for characterizing the plastic deformation of ceramics over a wide range of strain rates.