This chapter describes the phases and constituents present in iron-carbon steels in near-equilibrium conditions. It explains how to use phase diagrams to predict and manage the development of ferrite, austenite, cementite, and pearlite through controlled cooling. It discusses the transformations, grain structure, and properties associated with each phase and identifies the primary stabilizing elements. It includes several micrographs revealing various microstructural features and describes the processing route by which they were achieved. It explains how to estimate the volume fraction of iron-carbon phases in equilibrium and how to determine the amount of each phase that must be present to reach a desired composition. The chapter also discusses the phases associated with hypo- and hyper-eutectoid steels and presents more than a dozen micrographs, identifying important structural features along with cooling conditions and sample preparation procedures.

This chapter discusses the construction, interpretation, and use of ternary phase diagrams. It begins by examining a hypothetical phase space diagram and several corresponding two-dimensional plots. It then describes one of the most basic tools of metallurgy, the Gibbs triangle, and explains how to construct tie lines to analyze intermediate compositions and phases. It also discusses the use of three-dimensional temperature-composition diagrams, three- and four-phase equilibrium phase diagrams, and binary and ternary phase diagrams associated with the iron-chromium-nickel alloy system.