The conditions for the formation of amorphous alloys in the Fe-P-M (M
= Mo, V, Nb, Mn, Si) systems are studied in relation to metastable pha
se equilibria. The tendency for these alloys to amorphize and their th
ermal stability are found to depend on the features of metastable tran
sformations. A new metastable phase identified in the Fe-P-Si system b
inds P and Si in an iron-based complex, thus enhancing the thermal sta
bility of amorphous alloys.