Binary Phase Diagrams

There is a graphical construction that allows you to determine the chemical potentials of chemical species in solution:

Figure 2-4: A graphical construction of great importance.

This construction and the equality of chemical potentials results in the common tangent construction between several phases of heterogeneous solution in a binary alloy:

Figure 2-5: Common Tangent Construction

Which allows the construction of binary phase diagrams, for example:

Figure 2-6: Eutectic binary phase diagram

The two phase regions are composed of the limiting compositions on either side of the two-phase region on the phase diagram; the lever rule allows us to determine the fractions of each phase.

There are four main types of binary phase diagrams: Eutectic-type, Peritectic-type, Spinodal, and Lens. You should be able to draw these without too much effort.