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<p>In the last thirty years, several successful projects have been developed by sheet steel producers and researchers for the automotive sector, demonstrating steel’s capability to meet growing demands for greater safety and fuel efficiency through light-weighting of various vehicle structures. Quenching and partitioning (Q&amp;P) steels are an example of a recent development. They consist of a suitable combination of chemical composition and thermomechanical processing, exhibiting a good combination of strength and ductility, which permitted their use in a new generation of advanced high-strength steels (AHSS) for automobiles. In this way, this research employed physical and thermodynamic simulations, to develop a third-generation AHSS product using the Q&amp;P methodology. Three distinct Q&amp;P heat treatments were proposed for a CMnSi first-generation AHSS widely used in the automotive industry: (1) Q&amp;P after intercritical austenitizing (IA), (2) Q&amp;P after step quenching (SQ), and (3) Q&amp;P after complete austenitizing. The resulting microstructures were characterized by scanning electron microscopy, X-ray diffractometry, and transmission electron microscopy. The results revealed retained austenite fractions ranging from 6 to 10&#xa0;pct, with a predominantly blocky morphology observed in the Q&amp;P conditions following IA and SQ, and a film-like morphology in the Q&amp;P condition following complete austenitizing. Mechanical characterization was performed through tensile and fracture toughness tests. All resulting microstructures met the requirements for a third-generation AHSS. The Q&amp;P heat cycle after SQ presented the highest fracture toughness and a tensile product of strength and elongation (PSE) of 28&#xa0;GPa&#xa0;pct; a relatively high value for this simple steel chemical composition (CMnSi).</p>

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Effect of Q&P Heat Treatments on the Microstructure, Tensile Mechanical Behavior, and Fracture Toughness of a Commercial CMnSi Alloy Aiming to Obtain a Third-Generation AHSS

  • 期刊论文

  • 发表日期：

    2025年5月15日

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  • Charles H. X. M. Magalhães,
  • Leonardo B. Godefroid,
  • Geraldo L. Faria

摘要

In the last thirty years, several successful projects have been developed by sheet steel producers and researchers for the automotive sector, demonstrating steel’s capability to meet growing demands for greater safety and fuel efficiency through light-weighting of various vehicle structures. Quenching and partitioning (Q&P) steels are an example of a recent development. They consist of a suitable combination of chemical composition and thermomechanical processing, exhibiting a good combination of strength and ductility, which permitted their use in a new generation of advanced high-strength steels (AHSS) for automobiles. In this way, this research employed physical and thermodynamic simulations, to develop a third-generation AHSS product using the Q&P methodology. Three distinct Q&P heat treatments were proposed for a CMnSi first-generation AHSS widely used in the automotive industry: (1) Q&P after intercritical austenitizing (IA), (2) Q&P after step quenching (SQ), and (3) Q&P after complete austenitizing. The resulting microstructures were characterized by scanning electron microscopy, X-ray diffractometry, and transmission electron microscopy. The results revealed retained austenite fractions ranging from 6 to 10 pct, with a predominantly blocky morphology observed in the Q&P conditions following IA and SQ, and a film-like morphology in the Q&P condition following complete austenitizing. Mechanical characterization was performed through tensile and fracture toughness tests. All resulting microstructures met the requirements for a third-generation AHSS. The Q&P heat cycle after SQ presented the highest fracture toughness and a tensile product of strength and elongation (PSE) of 28 GPa pct; a relatively high value for this simple steel chemical composition (CMnSi).