Imaging Differences in the Electrical Conductivity of Metals by Microwave Microscopy Using a Coaxial Probe

Near-field scanning microwave microscopy using a coaxial probe has been theoretically and experimentally investigated in order to image differences in the electrical conductivity of metal samples. Experiments performed at 17.5 GHz $\boldsymbol{(\lambda=17.1\ \text{mm})}$ show that the graphite structure of ductile cast iron, whose characteristic dimension was of the order of tens of microns, can be successfully imaged. This result suggests that near-field scanning microwave microscopy technique proposed herein can provide a useful means of classifying the graphite structure in cast iron, which affects the mechanical properties of the metal.