The iron-carbon phase diagram illustrates the different phases and microstructures of iron and its alloys as carbon content varies. It shows how temperature and carbon concentration affect the formation of phases like ferrite, austenite, and cementite. This diagram is crucial for understanding the properties of steel and cast iron. In the diagram, specific regions indicate stable phases at given temperatures and carbon levels. For example, at lower carbon concentrations, ferrite is stable, while higher carbon levels lead to the formation of cementite. Understanding this diagram helps in predicting material behavior during processes like heat treatment.