Crystal Chemistry of Metastable Alloy Phases

Knowledge of the metastable crystalline alloy phases that can be prepared from the liquid or vapor by non-equilibrium methods is useful because the descriptive crystal chemistry of an alloy system should include metastable phases stable with respect to the components but unstable respective to other intermediate phases [1]. Alloy phases within a certain range of positive free energy of formation are also of interest, especially for systems without equilibrium phases. Accordingly, there have been some systematic “hunts” for metastable alloy phases (MAP's) that can be prepared by rapid liquid quenching, reviewed in Refs. 2–7. The principal results of these studies on disordered (element-like) and ordered MAP's and some additional data are presented here.