Incipient plasticity in metallic thin films

The authors have compared the incipient plastic behaviors of Al and Al–Mg thin films during indentation under load control and displacement control. In Al–Mg, solute pinning limits the ability of dislocations to propagate into the crystal and thus substantially affects the appearance of plastic instabilities as compared to pure Al. Displacement control allows for a more sensitive detection of such instabilities, as it does not require collective dislocation motion to the extent required by load-controlled indentation in order to resolve a yield event. This perception is supported by in situ transmission electron microscopy observations.