Kinetics of sigma phase formation in a Duplex Stainless Steel

Materials Research

Rodrigo Magnabosco¹ 

[1] ,Ignatian Educational Foundation Department of Mechanical Engineering São Bernardo do Campo SP ,Brazil

关键词: duplex stainless steels;    sigma phase;    phase transformations;    kinetics;   

DOI  :  10.1590/S1516-14392009000300012

来源: SciELO

【 摘 要 】

This work determines the kinetics of sigma phase formation in UNS S31803 Duplex Stainless Steel (DSS), describing the phase transformations that occur in isothermal aging between 700 and 900 ºC for time periods up to 1032 hours, allowing the determination of the Time-Temperature-Precipitation (TTP) diagram for sigma phase and proposing a model to predict the kinetics of sigma phase formation using a Johnson-Mehl-Avrami (JMA) type expression. The higher kinetics of sigma phase formation occurs at 850 ºC. However, isothermal aging between 700 and 900 ºC for time periods up to 1032 hours are not sufficient to the establishment of thermodynamic equilibrium. Activation energy for both nucleation and growth of sigma phase is determined (185 kJ.mol-1) and its value is equivalent to the activation energy for Cr diffusion in ferrite, indicating that diffusion of Cr is probably the major thermally activated process involved in sigma phase formation. The determined JMA type expression presents good fit with experimental data between 700 and 850 ºC.

【 授权许可】

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