Effect of thermal-expansion mismatch on thermomechanical behaviour of compacted graphite iron

Compacted graphite iron (CGI) attracted considerable attention in the automotive industry thanks to its excellent thermomechanical properties and cost-effectiveness. At microscale, the primary fracture mechanism in CGI involves interfacial damage and debonding between graphite inclusions and the metallic matrix, which can occur under high-temperature conditions due to the mismatch in the coefficients of thermal expansion of the constituents. This interfacial damage at the microscale can trigger macroscopic fractures in cast iron components subjected to pure thermal loading. While this phenomenon was widely studied in other composites, there is still limited detailed information available for CGI, particularly regarding the effect of complex morphology of its graphite particles. This research investigates the influence of graphite morphology and matrix behaviour on the thermomechanical performance of CGI at elevated temperatures. A set of three-dimensional finite-element models were developed, featuring unit cells with a single graphite inclusion embedded within a cubic metallic matrix. Elastoplastic behaviour was assumed for both phases in numerical simulations. The study focused on the response of CGI’s constituents to pure thermal loading, aiming to explore a link between inclusion morphology and fracture mechanisms. The findings aim to improve the understanding of how graphite morphology affects the behaviour of CGI under high-temperature conditions.