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<p>The increasing demand for fuel-efficient and lightweight vehicles has driven the development of advanced-high-strength steels (AHSS), particularly for electric vehicle (EV) applications. In this study, the microstructure and mechanical properties of a 3.5 wt.% medium-manganese steel (MMS) were investigated following intercritical annealing (IA) at 660, 700, and 740&#xa0;°C for 3&#xa0;minutes. The steel exhibited a multiphase microstructure comprising ferrite, retained austenite (RA), and thermally induced martensite depending on the IA temperature. EBSD analysis revealed maximum RA fraction (~7%) and recrystallization (~78%) at 700&#xa0;°C, which also corresponded to the most favorable mechanical performance with an ultimate tensile strength (UTS) of 1225&#xa0;MPa, 13% total elongation, and a UTS × elongation product of 15.93 GPa%. The IA-660&#xa0;°C sample showed superior ductility (18%) but lower UTS, while IA at 740&#xa0;°C led to the formation of thermal martensite, yielding high strength (1325&#xa0;MPa) but poor ductility (6%). The work hardening behavior and deformation-induced martensitic transformation were strongly influenced by the stability of retained austenite, which was controlled by the IA temperature. These findings highlight the potential of optimizing IA parameters to tailor strength–ductility synergy in medium-Mn steels for applications in automotive industries.</p>

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Microstructure and Mechanical Properties of Intercritically Annealed 3.5 wt.% Medium-Mn Steel

  • 期刊论文

  • 发表日期：

    2025年12月17日

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  • Isha Apurwa,
  • Ashok Kumar

摘要

The increasing demand for fuel-efficient and lightweight vehicles has driven the development of advanced-high-strength steels (AHSS), particularly for electric vehicle (EV) applications. In this study, the microstructure and mechanical properties of a 3.5 wt.% medium-manganese steel (MMS) were investigated following intercritical annealing (IA) at 660, 700, and 740 °C for 3 minutes. The steel exhibited a multiphase microstructure comprising ferrite, retained austenite (RA), and thermally induced martensite depending on the IA temperature. EBSD analysis revealed maximum RA fraction (~7%) and recrystallization (~78%) at 700 °C, which also corresponded to the most favorable mechanical performance with an ultimate tensile strength (UTS) of 1225 MPa, 13% total elongation, and a UTS × elongation product of 15.93 GPa%. The IA-660 °C sample showed superior ductility (18%) but lower UTS, while IA at 740 °C led to the formation of thermal martensite, yielding high strength (1325 MPa) but poor ductility (6%). The work hardening behavior and deformation-induced martensitic transformation were strongly influenced by the stability of retained austenite, which was controlled by the IA temperature. These findings highlight the potential of optimizing IA parameters to tailor strength–ductility synergy in medium-Mn steels for applications in automotive industries.