Micromechanical investigation of fracture behaviour in compacted graphite iron using the discrete element method

Compacted graphite iron (CGI) is widely used in engineering applications due to its excellent mechanical properties, thermal conductivity, and wear resistance. However, its heterogeneous microstructure, which consists of worm-like graphite embedded within a ferritic-pearlitic matrix, presents significant challenges in accurately predicting fracture behaviour and damage evolution. To address this gap, we develop a micromechanical simulation framework based on the discrete element method (DEM) for the first systematic investigation of tensile deformation and fracture in CGI. The model incorporates image-based microstructural reconstruction and is quantitatively validated against experimental results in terms of stress–strain response and crack path morphology. Based on this validated model, a comprehensive parametric study is performed to evaluate the influence of graphite morphology and spatial distribution. The results reveal that increasing graphite volume fraction and misaligned orientations are the dominant factors reducing strength, while larger aspect ratios and particle sizes promote damage localization. Furthermore, under microstructural randomness, particle size remains a key factor affecting failure modes. These findings provide mechanistic insights into microstructure-sensitive fracture of CGI that are difficult to obtain experimentally, and demonstrate the potential of DEM as a predictive tool for understanding microstructure-sensitive failure and guiding the design of high-performance cast iron components.