In physical chemistry, mineralogy or materials science, a phase diagram is a type of graph used to show the equilibrium conditions between the thermodynamically-distinct phases.
Phase Equilibria diagrams are one of the single most useful tools of a materials scientist and engineer. As maps of the temperature ranges and solubility limits of each known phase in the alloy system, including compounds, they are obviously useful to metal casters, heat treaters, ceramicists ... etc., and are an invaluable tool in alloy design, in the development of high-temperature superconductors and in investigations of practically any temperature dependent property.
DiagPlot is a software (freeware, cf. "download") developed and designed for engineers and students to easily plot phase equilibria diagrams for binary and ternary systems, 2D & 3D.