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<p>This study investigates the effect of intercritical annealing parameters on microstructure evolution and tensile behavior of lean medium-Mn steels with Silicon (Si) and Aluminum (Al) additions, namely Fe-0.2C-7Mn-3Si and Fe-0.2C-7Mn-3Al. The one-step intercritical annealing followed by air cooling was applied for the hot-rolled steel sheets with 3&#xa0;mm thickness, aiming to achieve an optimal strength–ductility balance at a cost-effective processing route. The austenite fraction was quantified by the x-ray diffraction (XRD) method, while the scanning electron microscope (SEM) and electron backscattering diffraction (EBSD) techniques were used to characterize the microstructure of the investigated steels. The optimum tensile properties obtained for steel 7Mn3Si were an ultimate tensile strength (UTS) of 1481.8&#xa0;MPa and total elongation (TE) of 29% with a product of strength and elongation (PSE) of 42.9&#xa0;GPa% at 630&#xa0;°C and 15&#xa0;min. The austenite morphology consisted of lath-like and globular in a moderate stability with a percentage of 56.5% and an average grain size of 1.13&#xa0;μm. The 7Mn3Al steel exhibited its best properties after intercritically annealing at 650&#xa0;°C for 30&#xa0;min, reaching a UTS of 943.6&#xa0;MPa, TE of 43%, and PSE of 40.6&#xa0;GPa%. This steel exhibited 60.4% austenite fraction with an average grain size of 1.19&#xa0;μm. The obtained results of this study confirm that both 7Mn3Si and 7Mn3Al steels can achieve a superior combination of strength and ductility. Therefore, these steels can be employed in the production of specific automobile parts according to the function, where either high strength or high ductility is required.</p>

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One-Step Intercritical Annealing of Lean Medium-Mn Steels with Either Si or Al Additions: Achieving High Strength–Ductility Combination for Automotive Applications

  • 期刊论文

  • 发表日期：

    2025年12月29日

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  • Esraa Kotb,
  • Mamdouh Eissa,
  • Hoda El-Faramawy,
  • Magdi Abadir,
  • Ahmed El-sheikh

摘要

This study investigates the effect of intercritical annealing parameters on microstructure evolution and tensile behavior of lean medium-Mn steels with Silicon (Si) and Aluminum (Al) additions, namely Fe-0.2C-7Mn-3Si and Fe-0.2C-7Mn-3Al. The one-step intercritical annealing followed by air cooling was applied for the hot-rolled steel sheets with 3 mm thickness, aiming to achieve an optimal strength–ductility balance at a cost-effective processing route. The austenite fraction was quantified by the x-ray diffraction (XRD) method, while the scanning electron microscope (SEM) and electron backscattering diffraction (EBSD) techniques were used to characterize the microstructure of the investigated steels. The optimum tensile properties obtained for steel 7Mn3Si were an ultimate tensile strength (UTS) of 1481.8 MPa and total elongation (TE) of 29% with a product of strength and elongation (PSE) of 42.9 GPa% at 630 °C and 15 min. The austenite morphology consisted of lath-like and globular in a moderate stability with a percentage of 56.5% and an average grain size of 1.13 μm. The 7Mn3Al steel exhibited its best properties after intercritically annealing at 650 °C for 30 min, reaching a UTS of 943.6 MPa, TE of 43%, and PSE of 40.6 GPa%. This steel exhibited 60.4% austenite fraction with an average grain size of 1.19 μm. The obtained results of this study confirm that both 7Mn3Si and 7Mn3Al steels can achieve a superior combination of strength and ductility. Therefore, these steels can be employed in the production of specific automobile parts according to the function, where either high strength or high ductility is required.