Probing Structure-Property Relationships in Cu-Ni and Cu-Zn alloys in Nanofoam Form with Nanoindentation

The properties of nanostructured materials can differ from their equivalent bulk material by an order of magnitude. At the nanometer scale structural characteristics start to play an important role, and size effects can become the predominant factor on the final property. Using a novel polymer templating method followed by heat treatment, we fabricated low density (sub-10%) nanofoams of Cu, Cu-Ni and Cu-Zn alloys with alloy concentration from 10at% to 25at%, ligament size and relative density. The microstructural characteristics were observed under electronic microscopy (SEM) and X-ray diffraction (XRD). The modulus and strength were determined using instrumented indentation tests to find the modulus and hardness of these materials. The linear association between parameters studied and the dependent variables (Modulus and hardness) was found using Pearson Correlation Coefficient (PCC). Relative density was found as one of the dominant parameters on the mechanical properties, showing significant decreases in strength and modulus around 6% relative density. The mechanical properties results are not only a consequence of the relative density; however, the combination of ligament size and strengthening mechanisms do significantly influence the result. The structure of nanofoams can be tailored to have desired outcomes by controlling the combination of foam chemistry, architecture, and density.