Indentation mechanics of Cu-Be quantified by an in situ transmission electron microscopy mechanical probe

In situ transmission electron microscopy was used to study, in real time, the sub-surface deformation taking place in Cu-Be alloy during nanoindentation. A twinned region of the material was indented with a sharp tungsten tip in a specially developed transmission electron microscopy (TEM) holder. A flexible hinge-based force sensor was used to measure the force on the indenter, and the force-displacement curve for the tip was obtained by tracking the tip in the sequential images of a TEM video of the indentation process. Step-like structures similar to 50 nm in size resulting from the tip surface roughness were observed to generate clusters of dislocations in the sample when they come in contact with the softer Cu-Be. With this setup, the forces and the mean pressure associated with such an individual deformation event in a nanostructured TEM sample were measured.