| In the paper,the effect of heat treatment and element component on the phase proportion of duplex stainless steel(DSS),the stochastic analysis of corrosion resistance on different phase proportion DSS,the effect of aging on the microstructure and property of DSS,and the effect of alternating voltage passivation on the Corrosion resistance of duplex stainless steel were investigated by XRD,SEM,XPS and electrochemical measurements.The phase proportions of two groups of samples were calculated accurately with stereology in order to study how to control the structure of DSS by controlling heat treatment and element component.The results of experiments show that the sample heated at 1100℃for 1 hour would attain the desired structure and the sample whose Creq=26.26 and Nieq=11.89 would attain the best properties.Using the stochastic analysis,a linear relationship was obtained between Epit and log(v) for DSS in a 3.5%NaCl aqueous solution at room temperature.When the phase proportion is about 1:1,the pitting potential is the noblest and the passive current is the lowest.The aging results show that compared with the specimens without aging,the secondary austenite precipitates after aging heat treatments during 450-750℃for 3 hours,but theσphase andχphase only precipitates at 750℃for 3h aging heat treatment;aging heat treatments lead to a rapid reduction of the plastic deformation capacity and notch bar impact values of DSS,while enhance the strength of the material at some temperature, besides this,aging at high temperature can improve the hardness of DSS; the fracture morphology of duplex stainless steel changes with the aging heat treatments and is different from each other;the aging behavior also cause a loss of corrosion resistance,especially at 750℃,because of the precipitation of a andχ.Potentiodynamic polarization and Ecorr vs t curves were obtained, together with electrochemical impedance spectroscopy(EIS) measurements, in order to understand the effects of alternating voltage(AV) passivation on the corrosion resistance of duplex stainless steel(DSS),SEM,EDS and XPS were employed to further investigate the influence of AV passivation on the properties of the passive film.The results of the electrochemical measuremenst showed that AV passivation significantly improved the corrosion resistance of DSS.SEM images indicated that the surface exhibited a unique morphology after AV passivation treatment,and XPS results suggested that AV passivation greatly increased the thickness of the passive film.Furthermore,significant chromium enrichment and a higher ratio of Fe3+/Fe2+ were observed in the passive film after AV passivation. Mott-Schottky results confirmed that AV passivation had a strong influence on the semiconducting properties of the passive film.
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