Tensile deformation of compacted graphite iron with realistic microstructures: effect of morphology of graphite inclusions

Compacted graphite iron (CGI) is a double-phase metal-matrix composite with graphite inclusions. Thanks to its good mechanical properties and thermal conductivity, CGI is extensively used in many applications, e.g., for brake drums and engine cylinder heads. Although the effects of graphite’s volume fraction and morphology on a macroscopic tensile response were investigated in recent years, the effect of real-life morphology of graphite inclusions obtained from micrographs and comparison with a case of their simplified elliptical shape is still missing. Building realistic 3D models requires a considerable amount of time due to extremely complicated geometries of graphite inclusions scattered throughout the metallic matrix. Therefore, developing a micro-scale finite-element model capable of investigating the performance of CGI is desirable. In this work, 2D micro-scale finite-element models are developed to (i) investigate the relations between mechanical properties and morphology of graphite inclusions and (ii) explore the effect of periodic boundary conditions on the domains studied. Images of CGI microstructure were obtained with scanning electron microscopy and ImageJ and CAD software were used to develop realistic and simplified models. The simulations were compared with experimental stress–strain curves from in-house experiments. The created models will assist in comprehending the mechanical behaviour of CGI.