Nanostructure and texture of a graphite spheroid in an Fe–C–Ce alloy

Graphite spheroids in Fe-C-Ce alloys have a duplex morphology, with an inner zone associated with direct precipitation from the liquid and an outer zone that developed during eutectic transformation. The inner zone was here investigated by transmission electron microscopy using electron diffraction and dark-field imaging. Diffraction patterns showed hk ellipses, but above all 002 spots indicating a probable 3D radial order associated with a structure composed of graphite crystallites. Dark-field imaging revealed a radial texture showing that spheroidal growth occurs in the inner zone through the simultaneous development of cells radiating from the substrate where graphite was nucleated. Cells with a similar orientation of the c -axis are adjacent and form angular sectors. This texture explains why radial features are consistently observed when graphite spheroids are viewed under polarized light, regardless of whether the spheroids have a single or duplex morphology.