MODELING THE CCT-DIAGRAM OF INTERMETALLIC PHASE PRECIPITATION IN DUPLEX STAINLESS-STEELS FROM ISOTHERMAL EXPERIMENTS

Background/aims: sigma-phase and other intermetallic phases in substan tial quantities may have detrimental effects on mechanical and corrosi on properties in stainless steels. Owing to experimental difficulties, the information describing the kinetics of intermetallic phase transf ormation is limited especially for non-isothermal processes. Methods: A computer model, which is based on an Avrami type of equation was dev eloped. The model uses information from isothermal experiments of sigm a-phase transformation and predicts the transformation kinetics during a cooling process. For instance, the computer program is capable of p redicting a continuous cooling transformation (CCT)-diagram. Results a nd conclusions: After optimisation based on direct measurements of vol ume fractions of sigma-phase in dilatometer specimens, the model was f ound to predict CCT-diagrams for sigma-phase transformation in duplex stainless steels with satisfactory accuracy. The program provides a po werful tool for optimising the manufacturing of such steels.