748K (475°C) Embrittlement of Duplex Stainless Steel: Effect on Microstructure and Fracture Behaviour

Cem Ornek, M. Grace Burke, Teruo Hashimoto, Dirk Engelberg

    Research output: Contribution to journalArticlepeer-review


    22Cr-5Ni duplex stainless steel has been aged at 748K (475°C) and the microstructure development correlated to changes in mechanical properties and fracture behaviour. Tensile testing of aged microstructures confirmed the occurrence of 475°C embrittlement, which was accompanied by an increase of strength and hardness and loss of toughness. Ageing caused spinodal decomposition of the ferrite phase, consisting of Cr-enriched α’’ and Fe-rich α’, and the formation of a large number of R-phase precipitates, with sizes between 50-400 nm. Fracture surface analyses revealed a gradual change of the fracture mode from ductile to brittle delamination fracture, associated with slip incompatibility between ferrite and austenite. Ferrite became highly brittle after 255 hours ageing, mainly due to the presence of precipitates, whilst austenite was ductile and accommodated most plastic strain. The fracture mechanism as a function of 475°C embrittlement is discussed in light of microstructure development.
    Original languageEnglish
    Pages (from-to)1653-1665
    JournalMetallurgical and Materials Transactions A - Physical Metallurgy and Materials Science
    Issue number4
    Early online date17 Jan 2017
    Publication statusPublished - 2017


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