Revealing and characterising solidification structure of ductile cast iron

Abstract

This study deals with the solidification and microsegregation processes of near eutectic ductile cast iron. A detailed analysis of old and new solidification models was made. Metallographic techniques, developed elsewhere by the authors, were used to reveal the solidification microstructure and macrostructure. The results allow a new solidification model to be proposed, where each solidification unit is a grain of eutectic austenite that has a dendritic substructure and contains a very large number of graphite nodules. A pattern of microsegregation exists inside each solidification grain, while no intergranular microsegregation has been detected. A procedure to characterise the solidification refinement was developed considering the location of the last to freeze areas.