A study of graphite morphology control in cast iron

The objectives of the research project were to gain a deeper understanding of the factors influencing the graphite morphology in cast iron; particularly the role of different solute elements in relation to the industrial manufacture of compacted graphite iron. A number of melt treatment processes were assessed for their abilities to produce low nodularity compacted graphite microstructures over a range of casting section thicknesses. In this respect, the magnesium-titanium method was found to be superior to treatment using cerium Mischmetall and calcium additives; and very promising results were obtained with methods using zirconium as a major constituent of the treatment alloy. Scanning electron microscopy, secondary ion mass spectrometry and X-ray microanalysis were used to study the structural characteristics of different cast iron microstructures and the elemental distributions of important solutes between the phases. This information was used to clarify the role of the main solute elements in graphite morphology control and to assess current graphite growth theories.