During aging at a temperature ranging from 650-950 ℃,the ferric matrix in duplex stainless steels undergoes various decomposition processes which could form the precipitates of the Sigma (σ) and Chi(χ) phases,as well as nitrides.It is well known that these precipitates lead to a reduction in creep ductility and adversely affect toughness and corrosion properties of steel.This experiment carried out qualitative and quantitative analyses of intermetallic phases and nitrides and established an analytical procedure,including specimen preparation,the choosing of the electrolyte and electrolytic systems,electrolytic isolation,wet chemical separation,and physical and chemical analysis,etc.The residues were collected by ultrasonic cleaning and filtration after galvanostatic electrolysis.Dynamic laser scattering sizer (DLS-sizer),scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to examine their structure,modality and size.Qualitative and quantitative analyses were performed by using X-ray diffraction (XRD),oxygen-nitrogen analyzer and wet chemical analysis.Furthermore,there is a discussion on the effect of isothermal treatment on precipitation that occurs at different temperatures for different periods of time.
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