Modelling simultaneous precipitation reactions in austenitic stainless steels

A physical model has been developed for simultaneous precipitation reactions in austenitic stainless steels, taking into account interactions between phases. Comparisons against experimental results show satisfying agreement, with the model successfully predicting the existence of transient phases that are often observed, but not predicted in equilibrium calculations. An analysis of σ-phase kinetics, especially the effect of grain size, supports the hypothesis that the formation of this phase depends more on the availability of high energy nucleation sites than on the driving force for its formation. The study underlines a lack of thermodynamic data for important phases in creep-resistant austenitic stainless steels.