Phase diagrams serve as a map to the phases present in an alloy at different temperatures and compositions. They also help in assessing mechanical properties, selecting heat treat temperatures, warning of possible solidification problems, and identifying routes for creating desired microstructures. This chapter familiarizes readers with the information contained in binary phase diagrams and the methods used to extract it. It explains how thermocouple measurements are used to determine liquidus, solidus, and eutectic reaction lines, how differential scanning calorimetry shows where phase reactions occur, and how x-ray diffraction identifies the actual phases present. It demonstrates the use of tie lines for determining phase composition at different temperatures and the application of the level rule to calculate phase fractions. It also discusses the CALPHAD method and presents computed binary phase diagrams that account for the presence of inclusions, oxygen content, and secondary phases.

This appendix contains sample problems with worked solutions pertaining to the use of binary phase diagrams. The problems require the determination of favorable temperatures and compositions, the amount and composition of phases in an alloy at a given temperature, the amount of a certain phase in different steels, and the microstructure developed in different alloys.

This chapter provides a brief overview of phase diagrams, explaining what they represent and how and why they are used. It identifies key points, lines, and features on a binary nickel-copper phase diagram and explains what they mean from a practical perspective. It also discusses the concept of equilibrium, the significance of Gibb’s phase rule, the theorem of Le Chatelier, and the use of the lever rule.

This chapter discusses the unique characteristics of isomorphous alloy systems. It begins with a review of the naming conventions for multi-component systems and the construction of a three-dimensional phase diagram for a two-component alloy system. It explains how phase diagrams can be constructed from time-temperature cooling curves and how they can be used to predict the phases present, their chemical compositions, and relative amounts. It also shows how phase diagrams can be modified to account for nonequilibrium cooling conditions.

This chapter provides an overview of a computational method, called CALPHAD, used for the study of phase equilibria in multicomponent systems. It describes the thermodynamic models and calculation techniques employed in the software and explains how it applies to complex alloys used in industry. It also provides examples showing how CALPHAD has been used to determine the formability of metallic glass, calculate the dilation of stainless steel during phase transformation, and predict the beta transus and approach curves of commercial titanium alloys.