Effect of Aging treatment on the Evolution of Precipitates in Super Duplex Stainless Steel
The precipitation behavior of precipitates in S32750 super duplex stainless steel was studied by aging treatment at 850℃.Thermo-Calc software was used to predict the precipitates and phase composition in tested steel.OM,SEM and EDS were used to analysis the microstructure and precipitates of S32750 super duplex stainless steel after different aging treatment.K-J-M-A model was used to analysis the kinetic of precipitation of σ phase.The results showed that the σ phase was preferred to precipitate at ferrite/austenite boundaries during the aging process at 850 ℃.There were two main steps to control the precipitation of σ phase:nucleation control and element diffusion control.In addition,χ phase and Cr2N phase also precipitated during aging treatment.χ was the sub-stable phase,precipitated in the early aging period,and finally transformed into σ phase with the prolongation of aging time.
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