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<p>The Ti–Mo–Nb ternary composite microalloying strategy was employed to enhance the strength of hot-rolled ferritic steel by introducing a high density of nanoscale composite precipitates within the ferrite matrix. Through a combination of experimental characterization and thermodynamic calculations, the segregation behavior of Ti, Mo, and Nb at the γ/α interface and the corresponding precipitation mechanisms of second-phase particles were systematically investigated. Furthermore, the influence of coiling temperature on the morphology and distribution of precipitates and their effect on mechanical properties was clarified. Results reveal that Ti, Mo, and Nb exhibit strong segregation tendencies and high solid solution content at the γ/α interface, which provides (Ti, Mo, Nb)C precipitates with a high precipitated driving force and nucleation rate. Compared with dislocation-induced nucleation in ferrite, the incubation period of (Ti, Mo, Nb)C at the γ/α interface is significantly shortened, leading to a precipitation onset approximately 12–18 orders of magnitude earlier. Although lowering the coiling temperature slightly extends the incubation period, the reduced ferrite transformation driving force shortens the step height of ferrite transformation, thereby decreasing the interphase precipitation spacing. As the coiling temperature decreases from 650 to 550&#xa0;°C, the precipitation strengthening increment increases from 239 to 306&#xa0;MPa, with the contribution of interphase precipitation rising from 72% to 95%, making it the dominant strengthening mechanism. The optimized steel exhibits an excellent combination of tensile strength of 755&#xa0;MPa, yield strength of 712&#xa0;MPa, and elongation to fracture of 22%.</p>

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Revealing interphase and random precipitation behaviors in ultra-high strength ferritic steel

  • 期刊论文

  • 发表日期：

    2026年7月9日

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  • Ru-Yang Han,
  • Geng-Wei Yang,
  • Wen Liang,
  • Hui-Hui Huang,
  • Guo-Jian Liu,
  • Wen Yan

摘要

The Ti–Mo–Nb ternary composite microalloying strategy was employed to enhance the strength of hot-rolled ferritic steel by introducing a high density of nanoscale composite precipitates within the ferrite matrix. Through a combination of experimental characterization and thermodynamic calculations, the segregation behavior of Ti, Mo, and Nb at the γ/α interface and the corresponding precipitation mechanisms of second-phase particles were systematically investigated. Furthermore, the influence of coiling temperature on the morphology and distribution of precipitates and their effect on mechanical properties was clarified. Results reveal that Ti, Mo, and Nb exhibit strong segregation tendencies and high solid solution content at the γ/α interface, which provides (Ti, Mo, Nb)C precipitates with a high precipitated driving force and nucleation rate. Compared with dislocation-induced nucleation in ferrite, the incubation period of (Ti, Mo, Nb)C at the γ/α interface is significantly shortened, leading to a precipitation onset approximately 12–18 orders of magnitude earlier. Although lowering the coiling temperature slightly extends the incubation period, the reduced ferrite transformation driving force shortens the step height of ferrite transformation, thereby decreasing the interphase precipitation spacing. As the coiling temperature decreases from 650 to 550 °C, the precipitation strengthening increment increases from 239 to 306 MPa, with the contribution of interphase precipitation rising from 72% to 95%, making it the dominant strengthening mechanism. The optimized steel exhibits an excellent combination of tensile strength of 755 MPa, yield strength of 712 MPa, and elongation to fracture of 22%.