A model for the multi-nodule eutectic grain microstructure evolution in spheroidal graphite iron

Deterministic and stochastic models that attempt to describe the solidification of spheroidal graphite (SG) iron are based on carbon diffusion calculation within a spherical aggregate made of one graphite spheroid and a surrounding austenite shell. However, experimental observations demonstrate that the eutectic structure of SG iron includes primary austenite dendrites as well as eutectic dendrites containing several nodules. The paper presents a new stochastic model that generates realistic calculated microstructures of the multi-nodule eutectic grains of SG iron. Deterministic laws are implemented with cellular automaton (CA) rules. Nucleation is assumed random and independent for graphite and austenite grains, but the growth of the nodules is closely related to the austenite growth through a stochastic process that defines the position of the nodules.