Nodule evolution of ductile cast iron during solidification

Abstract

Ductile cast irons are ferrous alloys in which precipitation of graphite in the form of spherical nodules areis embedded ina metal matrix to obtain ductility on the material. Despite of the importance of the shape of the nodules, the models proposed topredict the solidification of ductile irons assume a perfect spherical shape during the growing process up to the final solidificationof the material, which is proved not to be the case in all castings depending on the processing conditions. The influence of theprocess parameters on the geometry of the nodules in ductile irons was experimentally evaluated and a model to predict theevolution of nodules during solidification was proposed. The proposed model for growth predicts changes in the nodule count aswell as in the nodularity based on different laws for carbon diffusion according to the solid fraction, helping to understand thetrends found experimentally.