A new method for reliable determination of strain-rate sensitivity of low-dimensional metallic materials by using nanoindentation

Nanoindentation is increasingly used to determine the strain-rate sensitivity of nanocrystalline metallic thin films. However, traditional data analysis yields large uncertainty on displacements measured at low strain rates due to thermal drift. Here we use a new method that renders hardness insensitive to thermal drift. The method involves directly measuring contact stiffness and calculating the contact area from the measured stiffness and modulus. The new technique is validated through nanocrystalline Ni and nanotwinned Cu films and returns expected values.