Nano-scale orientation mapping of graphite in cast irons

• ACOM/TEM can be used to study the crystal orientation of carbon-based materials.
• A spheroid is formed by conical sectors radiating from a central nuclei.
• Misorientations exist within the conical sectors, defining various orientation domains.

A diametrical section of a graphite spheroid from a ductile iron sample was prepared using the focused ion beam-lift out technique. Characterization of this section was carried out through automated crystal orientation mapping in a transmission electron microscope. This new technique automatically collects electron diffraction patterns and matches them with precalculated templates. The results of this investigation are crystal orientation and phase maps of the specimen, which bring new light to the understanding of growth mechanisms of this peculiar graphite morphology. This article shows that mapping the orientation of carbon-based materials such as graphite, which is difficult to achieve with conventional techniques, can be performed automatically and at high spatial resolution using automated crystal orientation mapping in a transmission electron microscope.