Pure iron can have two different crystal ... the micro-structure of the alloy is a solid-state process: Austenite <-> Ferrite + Cementite Austenite is stable above 727 C and is an interstitial solid ...

(Top diagram) Diamond is metastable at room temperature and has a diamond cubic crystal structure. (Lower diagram) The diamond cubic structure is a face-centered-cubic lattice with a basis of two ...