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<p>Advanced high-strength steels (AHSSs) are developed through engineered multiphase microstructures to achieve superior mechanical performance. In this study, a medium-silicon low-alloy steel was subjected to two different heat treatment processes—dual-phase (DP) and Quenching and Partitioning (Q&amp;P)—to investigate the influence of microstructure on mechanical behavior. The DP microstructure was produced by step quenching in the ferrite–austenite region followed by water quenching, while Q&amp;P specimens were processed by rapid quenching below MS temperature and partitioning above it. Quantitative phase analysis using EBSD and XRD revealed that the DP samples contain approximately 68% martensite and 32% ferrite, while Q&amp;P samples feature a complex microcomposite structure consisting of tempered martensite, fresh martensite, carbide-free bainite, and ~ 18% retained austenite. Mechanical testing showed a significant improvement in the strength–ductility trade-off for Q&amp;P specimens, where the product of ultimate tensile strength and total elongation (PSE) increased from 2.4 GPa.% for DP specimens to 16.3 GPa.% for Q&amp;P specimens. Despite the presence of retained austenite, its transformation to martensite during deformation was only partially responsible for strain hardening, indicating a complex interaction among the microphases. The Q&amp;P specimens also exhibited enhanced toughness, with Charpy impact energy increasing from 3.5 J (DP) to 29 J. These results demonstrate that tailored microcomposite architectures through Q&amp;P treatment can significantly enhance the mechanical performance of low-alloy steels.</p>

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Microstructure and Mechanical Behavior of a Medium-Silicon Low-Alloy Steel: A Comparative Study of Ferrite–Martensite Dual-Phase and Austenite–Martensite Q&P Conditions

  • 期刊论文

  • 发表日期：

    2026年2月23日

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  • Ali Khajesarvi,
  • Seyyed Sadegh Ghasemi Banadkouki

摘要

Advanced high-strength steels (AHSSs) are developed through engineered multiphase microstructures to achieve superior mechanical performance. In this study, a medium-silicon low-alloy steel was subjected to two different heat treatment processes—dual-phase (DP) and Quenching and Partitioning (Q&P)—to investigate the influence of microstructure on mechanical behavior. The DP microstructure was produced by step quenching in the ferrite–austenite region followed by water quenching, while Q&P specimens were processed by rapid quenching below MS temperature and partitioning above it. Quantitative phase analysis using EBSD and XRD revealed that the DP samples contain approximately 68% martensite and 32% ferrite, while Q&P samples feature a complex microcomposite structure consisting of tempered martensite, fresh martensite, carbide-free bainite, and ~ 18% retained austenite. Mechanical testing showed a significant improvement in the strength–ductility trade-off for Q&P specimens, where the product of ultimate tensile strength and total elongation (PSE) increased from 2.4 GPa.% for DP specimens to 16.3 GPa.% for Q&P specimens. Despite the presence of retained austenite, its transformation to martensite during deformation was only partially responsible for strain hardening, indicating a complex interaction among the microphases. The Q&P specimens also exhibited enhanced toughness, with Charpy impact energy increasing from 3.5 J (DP) to 29 J. These results demonstrate that tailored microcomposite architectures through Q&P treatment can significantly enhance the mechanical performance of low-alloy steels.