On the Morphology Variation of Graphite in Ductile Cast Iron through Severe Plastic Deformation

Abstract

For decades, researchers have been concerned about the formability of manufactured wrought cast iron, with brittleness being a major issue in these alloys. To address this, the ferrite phase has been identified as a suitable matrix for cast iron deformation due to its ability to provide satisfactory ductility and avoid brittle limitations. In this study, machined parts of ductile cast iron were subjected to an annealing process at approximately 900°C for 1 h before undergoing hot plastic deformation with varying degrees of reduction. The deformation was carried out using a cylinder-covered hot compression (CCC or CCHC) technique. The primary objective of this study is to gain a microscopic understanding of hot plastically deformed ductile cast iron and propose a mathematically formulated flow strain that takes into account the contributions of the microstructure’s constituent phases. This analysis aims to provide a comprehensive characterization of deformed graphite within the microstructure. Optical microscopy (OM) and scanning electron microscopy (SEM) were employed to obtain results for the characterization. The findings revealed that as the reduction increased, spheroidal graphite tended to transform into a lamellar structure, resulting in diverse properties. Additionally, a microhardness test was conducted to assess the variation in mechanical properties throughout each deformation step.