Morphology Evolution of Graphite in Ductile Iron during Deformation

The present study systematically investigates the evolution of graphite morphology in ductile iron under different deformation parameters. The results indicate that the deformation of graphite in ductile iron is closely related to deformation parameters and the microstructure of surrounding matrix. The morphology of graphite in ductile iron transforms from spherical to elliptical and then to flake shape with the increase of strains. The deformation degree of graphite also increases with the increase in strain rates. Additionally, graphite embedded into austenite exhibits a greater degree of deformation compared to graphite embedded into ferrite under the same deformation parameters. This is mainly because the stress was almost completely transferred and loaded onto the graphite due to the strongly bonded interface of austenite-graphite in the deformation process. Notably, the graphite embedded into ferrite undergoes minimal deformation, especially when compressed at low strain rates. This behavior is associated with the friction-sliding interface between ferrite and graphite, which results in low flow stress applied to the graphite in the deformation process.