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<p>The steels used in the automobile sectors must possess an attentive balance between strength and ductility to maintain the structural integrity of vehicles and achieve intricate designs. At the same time, there is a continuous drive to reduce the weight of the passenger car to reduce the carbon footprint, while keeping passenger safety a top priority. The amount of weight reduction achievable in traditional high-strength steels is limited, and in addition, these steels have limited ductility, formability, and crashworthiness. A new austenitic lightweight steel has therefore been developed in the present work with a composition range of Fe–(10–30)Mn–(1–12)Al–(0.4–1.8)C–(0–9)Cr–(0–3)Si primarily for automotive applications. The mechanical properties and deformation mechanisms of lightweight steels are significantly affected by their stacking fault energy (SFE) and density. Precise prediction of the SFE is crucial for optimizing compositions that provide a balance of high strength, ductility, and specific weight.&#xa0;The present work aims to find an appropriate model for calculating the SFE of Fe–Mn–Al–C–Cr–Si lightweight steels. We discussed the means of estimating SFE through models based on thermodynamics theory and experiments. Based on the Olson–Cohen thermodynamic model, we calculated the SFE of some Fe–Mn–Al–C–Cr–Si steels with the corrected parameters of the model. Density calculations were performed by using an extended empirical formula. The impact of alloying elements on overall density was assessed by integrating their atomic masses and their effects on the molar volume of the&#xa0;austenite phase. Based on these model calculations, a Fe–Mn–Al–Cr–Si–C steel has been developed and thermo-mechanically treated in this work. Detailed microstructural characterization of the steel was done using SEM, XRD, and EBSD techniques, revealing the austenite formation. The SFE of the alloy is estimated to be 61.78&#xa0;mJ/m<sup>2</sup> in the thermodynamic model, and it matches well with that obtained from the XRD micro-strain method (62.68&#xa0;mJ/m<sup>2</sup>). The newly designed alloy has a yield strength of 426 ± 4&#xa0;MPa, an ultimate tensile strength of 744 ± 15&#xa0;MPa, and an elongation of 75 ± 3 pct with excellent features observed in the d<i>σ</i>/d<i>ε</i> <i>vs.</i> true stress curves.</p>

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Design and Development of a Lightweight Steel Through Computational Thermodynamics Approach and Experiments

  • 期刊论文

  • 发表日期：

    2025年7月1日

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  • Shetti Swamy,
  • Appala Naidu Gandi,
  • Sk Md Hasan

摘要

The steels used in the automobile sectors must possess an attentive balance between strength and ductility to maintain the structural integrity of vehicles and achieve intricate designs. At the same time, there is a continuous drive to reduce the weight of the passenger car to reduce the carbon footprint, while keeping passenger safety a top priority. The amount of weight reduction achievable in traditional high-strength steels is limited, and in addition, these steels have limited ductility, formability, and crashworthiness. A new austenitic lightweight steel has therefore been developed in the present work with a composition range of Fe–(10–30)Mn–(1–12)Al–(0.4–1.8)C–(0–9)Cr–(0–3)Si primarily for automotive applications. The mechanical properties and deformation mechanisms of lightweight steels are significantly affected by their stacking fault energy (SFE) and density. Precise prediction of the SFE is crucial for optimizing compositions that provide a balance of high strength, ductility, and specific weight. The present work aims to find an appropriate model for calculating the SFE of Fe–Mn–Al–C–Cr–Si lightweight steels. We discussed the means of estimating SFE through models based on thermodynamics theory and experiments. Based on the Olson–Cohen thermodynamic model, we calculated the SFE of some Fe–Mn–Al–C–Cr–Si steels with the corrected parameters of the model. Density calculations were performed by using an extended empirical formula. The impact of alloying elements on overall density was assessed by integrating their atomic masses and their effects on the molar volume of the austenite phase. Based on these model calculations, a Fe–Mn–Al–Cr–Si–C steel has been developed and thermo-mechanically treated in this work. Detailed microstructural characterization of the steel was done using SEM, XRD, and EBSD techniques, revealing the austenite formation. The SFE of the alloy is estimated to be 61.78 mJ/m2 in the thermodynamic model, and it matches well with that obtained from the XRD micro-strain method (62.68 mJ/m2). The newly designed alloy has a yield strength of 426 ± 4 MPa, an ultimate tensile strength of 744 ± 15 MPa, and an elongation of 75 ± 3 pct with excellent features observed in the dσ/dε vs. true stress curves.