Modeling of deleterious phase precipitation during isothermal treatments in superduplex stainless steel
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The deleterious constituents σ, χ, and eutectoid γ2 can precipitate during hot forming and welding operations in superduplex stainless steels. In this study the precipitation of these phases in superduplex UNS S32750 was investigated. Two materials with similar composition and quite different grain sizes were used in the study. Specimens were subjected to isothermal treatments in the 800–950 °C temperature range for time periods up to 240 min. Under these conditions, quantifications of deleterious phases by light optical microscopy were carried out in order to model the precipitation kinetics of these deleterious constituents. A sigmoidal equation, similar to the one developed by Johnson–Mehl–Avrami was fitted to all the analyzed temperatures. Precipitation velocity was evaluated so as to compare the kinetics of deleterious phases in the two materials. The activation energies for precipitation were calculated based on Arrhenius equation.
KeywordsFerrite Austenite Aging Temperature Sigmoidal Function Duplex Stainless Steel
The authors would like to thank CAPES, FAPERJ, and CNPq for their financial support which made this work possible.
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