ISIJ International
Online ISSN : 1347-5460
Print ISSN : 0915-1559
ISSN-L : 0915-1559
Regular Article
Prediction of Precipitation Sequences within Grains in 18Cr–8Ni Austenitic Steel by Using System Free Energy Method
Yoshiaki TodaFujio Abe
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2009 Volume 49 Issue 3 Pages 439-445

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Abstract

The applicability of theoretical energy analysis to the evolution of microstructures in heat-resistant steels was explored by using the system free energy method to predict the precipitation of M23C6 and σ phase within grains in 18Cr–8Ni austenitic steels. The chemical free energy of Fe–C–Cr–Ni quaternary steel and the interfacial and elastic strain energies between austenitic (γ) matrix and the M23C6 and σ phase were estimated for the system free energy of microstructures wherein coherent or incoherent M23C6 and the incoherent σ phase precipitated within γ grains. By identifying the minimum-energy path through a determination of system free energy hierarchies, the precipitation initiation curves of precipitates in Fe–0.07C–18.95Cr–9.57Ni steel for temperatures between 823–973 K were theoretically predicted. The calculated curves agreed well with experimental results for Type 304H austenitic steels; this suggests that the system free energy method is suitable for predicting the evolution of microstructures in heat-resistant steels.

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© 2009 by The Iron and Steel Institute of Japan
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