Effect of initial microstructure on superplasticity in ultrafine grained 18Cr-9Ni stainless steel

Toshihiro Tsuchiyama, Yoshikazu Nakamura, Hideyuki Hidaka, Setsuo Takaki

    Research output: Contribution to journalArticlepeer-review

    8 Citations (Scopus)

    Abstract

    Ultrafine grained austenitic structure was obtained in 18Cr-9Ni stainless steel by thermomechanical treatment using reversion from deformation-induced martensite. The superplastic deformation behavior was investigated at 923 K for the steels containing various amounts of retained martensite particles in the initial structure before tensile testing. The retained martensite was effective for suppressing grain growth of austenite and necessary for the superplasticity although it was thermodinamically unstable phase and gradually decreased its volume fraction with superplastic deformation. Therefore, the superplastic elongation was strongly dependent on the initial volume fraction of the retained martensite. The total superplastic elongation was enlarged with increasing the initial amount of martensite, and the maximum elongation of about 270% was obtained when the volume fraction was controlled to be around 10 vol%. However, the increase in elongation was leveled off in the range above 15 vol% martensite. The effect of the retained martensite on the superplasticiy was discussed in connection with the changes in volume fraction of the martensite, austenite grain size and deformation mechanism.

    Original languageEnglish
    Pages (from-to)2259-2263
    Number of pages5
    JournalMaterials Transactions
    Volume45
    Issue number7
    DOIs
    Publication statusPublished - Jul 2004

    All Science Journal Classification (ASJC) codes

    • Materials Science(all)
    • Condensed Matter Physics
    • Mechanics of Materials
    • Mechanical Engineering

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