3-D Analysis of Graphite Nodules in Ductile Cast Iron Using FIB-SEM

Ductile cast iron samples were analysed in a Focused Ion Beam Scanning Electron Microscope, FIB-SEM. The focussed ion beam was used to carefully remove layers of the graphite nodules to reveal internal structures in the nodules. The sample preparation and milling procedure for sectioning graphite nodules is described and ef-fects of preparation methods discussed. It was found that nodules contain different types of inclusions. These were analysed for chemical composition and crystallography using energy dispersive spectrometry (EDS) and electron back-scatter patterns (EBSP). Location of inclusions inside the nodules, their orientation in relation to the graphite and the chemistry of the inclusions is analysed and described. Formation of the structures during solidification and subsequent cooling to room temperature is discussed.