This appendix includes two annotated iron-carbon (Fe-C) phase diagrams. One is a poster-size diagram showing iron-carbon phases up to 7 wt% C along with representative microstructures. The other diagram is close-up view showing the phases that occur from 0 to 1.2 wt% C. It also includes labels identifying the microconstituents that form in plain carbon steels under rapid quenching conditions.