The iron-carbon system is one of the most important alloy systems in engineering, forming the basis for understanding steels and cast irons. It describes how varying amounts of carbon, when combined with iron and subjected to different temperatures, result in distinct phases and microstructures such as ferrite, austenite, cementite, and pearlite. These structures determine critical material properties like hardness, strength, ductility, and machinability.
The iron-carbon phase diagram allows us to visualize how these phases form and transform under different thermal conditions, guiding decisions in heat treatment, alloy selection, and processing. Key transformations—such as the eutectoid reaction that forms pearlite from austenite—are central to how steels behave in real-world applications. By studying the iron-carbon system, we gain insight into how small changes in composition and temperature can lead to significant differences in material performance.