Linking cooling conditions, pearlite characteristics, and mechanical properties in pearlitic ductile cast iron: experimental and simulation insights

• A strong correlation was found between the representative cooling rate of eutectoid phase transformation and the characteristics of the pearlite matrix in a fully pearlitic ductile cast iron. • The yield limit found to be strongly dependent on the interlamellar spacing of the pearlite matrix, following a modified Hall-Petch relationship. • In regions of higher strain, the graphite morphology is the dominant factor influencing mechanical properties under static loading. • Microstructure-informed simulation provides insights into how interlamellar spacing affects yield strength, highlighting the crucial role of pearlite fineness in yielding behavior. Microstructural features of ductile cast iron (DCI), including graphite morphology and the pearlitic matrix, are influenced by solidification and subsequent eutectoid transformation and can be effectively tailored through the cooling conditions. While the relationship between pearlite characteristics and mechanical properties is well established for pearlitic steels, the specific contribution of the pearlitic matrix to the mechanical response of DCI has received limited attention. In this study, fully pearlitic DCIs were cast under various cooling rates between 0.1 to 0.34 K/s, enabling systematic variations in microstructure to be correlated with changes in mechanical properties. The resulting interlamellar spacing (ILS) of the pearlite matrix ranged from 291 to 564 nm and was associated with an approximately 70 MPa difference in yield strength. A modified Hall-Petch-type relationship was formulated to describe the dependence of yield strength on ILS. To support predictive capability, representative volume elements were generated from optical micrographs and micromechanical simulations were conducted to isolate the effect of varying ILS on yield strength. The simulation results showed excellent agreement with the experiments, confirming that the ILS predominantly governs the onset of plastic deformation and that pearlite refinement is a key controlling factor for the yield strength of pearlitic DCI.