In Situ TEM Observations of Dislocation and Twinning Activities of Mg via Nanoindentation

Dislocations and deformation twinning are two important deformation mechanisms of Mg. In this work, we performed in situ nanoindentation experiment on a Mg sample. 500 nm thin windows were created using the focused-ion beam technique in the sample. This thickness allows for electron transparency and avoids excessive foil bending during indentation. The indentation was performed using the PI-95 in situ picoindenter equipped with a cube-corner tip. During loading, dislocations were first activated and a well-defined plastic zone was observed. At a later stage, extension twinning was activated. It was interesting to note that both dislocation and twinning retracted during unloading, highlighting the effect of elastic stress on the dislocation and twinning behavior.