Microstructural change during isothermal aging in high manganese austenitic steels

Yoshinori Ono, Toshihiro Tsuchiyama, Setsuo Takaki

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    Microstructural change during isothermal aging has been investigated in 13%Mn-0.9%C and 22%Mn-0.6%C steels by means of optical and electron microscopy and X-ray diffractometry. High manganese austenitic steels undergo three kinds of reactions during isothermal aging; (Circled digit one sign) grain boundary precipitation of carbide, (Circled digit two sign) precipitation of platelet carbide within austenite (γ) grains and (Circled digit three sign) formation of lamellar structure through eutectoid transformation (γ→ferrite (α) + carbide). In 13%Mn-0.9%C steel, all of the reactions occur and the carbide concerning the reactions is M 3C in any case. On the other hand, in 22%Mn-0.6%C steel, only two of them occur ; grain boundary precipitation of M 23C 6 carbide (not M 3C) and the eutectoid transformation (γ→ α + M 3C). Besides, both of the two reactions in 22%Mn-0.6%C steel were effectively suppressed due to the chemical composition ; high Mn and low C content. Eutectoid transformation proceeds by being supplied carbon from untransformed γ, so that this results in the shortage of carbon in untransformed γ during isothermal aging and the γ phase undergoes γ→ε (hcp) martensitic transformation on the following cooling.

    Original languageEnglish
    Pages (from-to)67-72
    Number of pages6
    JournalTetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan
    Issue number4
    Publication statusPublished - 1998

    All Science Journal Classification (ASJC) codes

    • Condensed Matter Physics
    • Physical and Theoretical Chemistry
    • Metals and Alloys
    • Materials Chemistry


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