Electron Microscopical Observations of Graphite in Cast Irons

Abstract

ABSTRACTGraphite flakes and spheroids, extracted from rare-earth treated cast irons, have been examined using electron microscopy. Transmission microscopy has been used to investigate the defect structure of flakes and to demonstrate the concentric aromatic shell structure of spheroids. Each spheroid is shown to possess a rare-earth containing core or nucleus.High resolution lattice images are presented as evidence for the presence of amorphous regions within flake graphite crystals. For spheroidal graphite, the lattice images indicate a greater degree of crystalline perfection. In addition, they suggest:1) The presence of intercalation structures2) The presence of an amorphous phase, on the graphite-iron interface, from which crystalline graphite forms at growth sites.The implications for possible mechanisms of graphite crystallization are discussed.