Work hardening behaviour in banded dual phase steel structures with improved formability

Bernard Ennis, C. Bos, M.P. Aarnts, Peter Lee, Enrique Jimenez-Melero

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    Abstract

    In this work, we show how the presence of microstructural banding and segregation affects the work-hardening behaviour of a dual phase steel with improved formability. This steel contains chemical segregation inherited from the casting process. Our previously developed 3D cellular automaton model allowed us to design thermo-mechanical processes to either promote or suppress banding. The bands are properly described as in-plane sheets of martensite grains. Mechanical testing data revealed a significant reduction in tensile strength in banded structures for a similar level of ductility. The work-hardening behaviour in the pre-yield regime, including the yield strength itself, is not correlated to the incidence of segregation and/or microstructural banding. The reduction in ultimate tensile strength in banded structures stems from a reduced work-hardening capacity in the post-yield regime. This is due to increased austenite stability in the banded steels, coupled to the anisotropic strain localisation in the ferritic matrix between martensite bands.
    Original languageEnglish
    Pages (from-to)278-286
    JournalMaterials Science and Engineering A
    Volume713
    Early online date21 Dec 2017
    DOIs
    Publication statusPublished - 2018

    Keywords

    • Mechanical characterization
    • hardening
    • Steel
    • Austenite
    • Martensite
    • Thermo-mechanical processing

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