Growth Stages and Hexagonal-Rhombohedral Structural Arrangements in Spheroidal Graphite Observed in Ductile Iron
Crystallographic structures of spheroidal graphite particles (graphite nodules) were examined using transmission electron microscopy (TEM). Structures of graphite nodules were investigated relative to different stages of nodule growth in ductile iron. Curved graphene layers were observed during the early growth of the graphite nodules. Thin layered stacking faults give rise to streaking in the basal reflections, which give rise to curvature of the nodule and growth steps on the surface. Columnar substructures consisting of parallel peripheral subgrains were found in the outside region of graphite nodules that were formed during the intermediate growth stage. Straight planar graphene layers were observed in the columnar substructures. Crystallographic orientation of graphite showed little change through the subgrain and the c-axes of multiple subgrains in a single columnar substructure were parallel. A method for characterizing the crystal structures of graphite based on the selected area diffraction pattern was introduced. Both hexagonal structure and rhombohedral structure were found in the spheroidal graphite particles. Possible crystallographic defects associated with hexagonal-rhombohedral structure transition were discussed.
J. Qing et al., "Growth Stages and Hexagonal-Rhombohedral Structural Arrangements in Spheroidal Graphite Observed in Ductile Iron," Carbon, vol. 116, pp. 456-469, Elsevier Ltd, May 2017.
The definitive version is available at http://dx.doi.org/10.1016/j.carbon.2017.01.063
Materials Science and Engineering
Keywords and Phrases
Ductility; Graphene; High resolution transmission electron microscopy; Stacking faults; Crystallographic defects; Crystallographic orientations; Crystallographic structure; Hexagonal structures; Rhombohedral structures; Selected area diffraction patterns; Spheroidal graphite; Structural arrangement
International Standard Serial Number (ISSN)
Article - Journal
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