ABSTRACT
A system consisting of two components is called a binary system or two-component system. The general two component system is controlled by three variables (pressure, temperature and composition) and it requires a three dimensional model. This chapter provides a phase diagram for a condensed binary system of the simple eutectic-type. This is a "composition vs. temperature" diagram with composition on the abscissa and temperature on the ordinate. The simple binary eutectic system is ideal for the introduction of quantitative calculations by the Lever Rule. The microstructure of liquid and crystalline phases or combinations of crystalline phases is extremely important during the experimental construction of a binary phase diagram, especially at certain critical temperatures or compositions. In binary systems, compounds are composed of various ratios of the two end members or the basic components of the system. The thermal behavior of intermediate compounds is of three basic types, congruent melting, incongruent melting or dissociation.
