There are four major uses of alloy phase diagrams:

This happens at just above the freezing temperature (0.01☌) and 0.006 atm.

For example, the water phase diagram describes a point (triple point) where water can coexist in three different phases at the same time. The diagram describes the suitable conditions for two or more phases to exist in equilibrium. Phase diagrams are graphical representations of the phases present in an alloy at different conditions of temperature, pressure, or chemical composition. III Different Phases What Are Phase Diagrams?