The iron-carbon phase diagram shows the equilibrium phases that exist at different temperatures for iron-carbon alloys. It includes three main phase transformations: the peritectic reaction where liquid transforms to austenite above 1400°C, the eutectic reaction where liquid transforms to austenite and cementite at 1130°C, and the eutectoid reaction where austenite transforms to ferrite and cementite at 723°C. The diagram is used to understand the microstructures that form during cooling of steels based on their carbon content, such as mixtures of ferrite and pearlite for eutectoid steels or ferrite/cementite for hypoeutect