Publisher Summary This chapter discusses the thermal analysis in metallurgy. Thermal analysis techniques that have been used in a wide variety of applications in metallurgy, are thermogravimetry (TG), differential thermal analysis (DTA), and differential scanning calorimetry (DSC). Equilibrium relationships between substances in different states, or between reactants and reaction products, have been traditionally expressed as phase diagrams correlating temperature and composition. The technique and the solidification are monitored under controlled conditions in the differential thermal analyzer, and then the sample is quenched at a certain moment to arrest the microstructure for further examination. Theoretical calculations based on available data of the binary systems are also carried out, taking into consideration the interaction between different phases.