Abstract Scope |
Graphite formation was investigated after the solidification of molten metal alloys to determine the conditions required to produce flakes, spheres, and vermicular structures. The size, shape, and spacing of graphite within a solidified structure directly impacts the strength, ductility, and thermal conductivity of metals, alloys, and composites materials containing it. Electromagnetic induction (EMI) and electromagnetic levitation (EML) heating were used to process bulk molten alloys of Fe-C, Fe-C-Si, Ni-C, Ni-C-Si, and Ni-C-Mg compositions. Graphite microstructures were examined in the droplet surface and interior and it was found that graphite flakes were promoted by increasing concentration of silicon and slower cooling rates, while spherical graphite was promoted by increasing the concentration of magnesium and faster cooling rates. Vermicular graphite occurred as an intermediary between conditions required to produce flake and spherical graphite. |