Precipitation of sigma phase in duplex stainless steel and recent development on its detection by electrochemical potentiokinetic reactivation:A review

Abstract The precipitation of sigma (σ) phase in the ferritic/austenitic duplex steel (DSS) results in the deterioration of mechanical intensity and corrosion resistance. After overviewing the temperature-time precipitation kinetic of secondary phases, this paper summarized the precipitation behavior of σ phase from the aspects of the mechanism, nucleation site, orientation relation, cooling rate, and phase composition. It is articulated that the preformed nitrides, carbides, and χ phase play the role of preparing regions containing low content C and N at their surroundings for σ nucleation rather than as the role as the nucleus of σ phase. Finally, the detection methods of σ phase including the recent use of electrochemical potentiokinetic reactivation (EPR) were introduced, and a prospect with the critical issues on futural DSS research was summarized.