AbstractThe thermodynamic predictions of microstructures in the multicomponent alloys used for duplex stainless steels are discussed in detail in this paper. The production of the duplex ferrite–austenite microstructure by high temperature (1323–1423 K) annealing is considered. Phase diagrams are calculated for Fe–Cr–Ni ternary alloys and the more complex multicomponent systems. It is shown that there is good agreement between the predictions of the thermodynamic models and the measurements carried out on heat treated alloys. The low temperature aging behaviour of Fe–Cr–Ni ternary alloys is discussed and the limitations of activation energy approaches to the modelling of the aging process in these alloys are shown.MST/1201