Investigation of thermally activated deformation in amorphous PMMA and Zr-Cu-Al bulk metallic glasses with broadband nanoindentation creep

The development of nanoindentation test systems with high data collection speeds has made possible a novel type of indentation creep test: broadband nanoindentation creep (BNC). Using the high density of data points generated and analysis techniques that can model the instantaneous projected indent area at all times during a constant-load indentation experiment, BNC can reveal materials properties across a range of strain rates spanning up to five decades (10⁻⁴–10 s⁻¹). BNC experiments aimed at measuring activation parameters for plasticity were conducted on three systems: two Zr-based bulk metallic glasses and poly-(methyl methacrylate) (PMMA). The results give insight into the operation of the deformation mechanisms present in the test materials, including the dependence of the deformation rate on the hydrostatic component of the stress for PMMA and the form of the activation energy function for the metallic glasses.