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<p>In this study, we designed two types of ultra-high-strength steels (UHSSs), namely, Nb-Ti and Nb-V microalloyed UHSSs, via a quenching-tempering process. Based on the microstructure and mechanical properties, the strengthening mechanisms of the steels were discussed. The results indicated that both steels achieved ultra-high tensile strength levels exceeding 2000 MPa after quenching. After tempering at 500-600&#xa0;°C, a large number of martensite packets appeared, significantly reducing the strength and increasing the total elongation. The strength levels are sustained at 800-1100 MPa with the total elongation ranging from 12 to 18%. The (Nb, Ti)(C, N), (Nb, V)(C, N), and Nb(C, N) carbides formed in the Nb-Ti and Nb-V microalloyed UHSSs grow in an ordered face-centered cubic structure. The strengthening mechanisms of the two experimental steels include solution strengthening, fine grain strengthening, dislocation strengthening, and precipitation strengthening. The predominant strengthening mechanism is dislocation strengthening. Additionally, the larger precipitates in the Nb-Ti steel primarily pin dislocations at grain boundaries, contributing to grain refinement, while the finer precipitates in the Nb-V steel enhance dislocation density and precipitation hardening, leading to superior overall strength.</p>

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Mechanical Properties and Nanoparticle Precipitation Behavior of Nb-Ti and Nb-V Ultra-High-Strength Microalloyed Steels

  • 期刊论文

  • 发表日期：

    2025年5月2日

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  • Xinwei Wang,
  • Renbo Song,
  • Haotian Chen,
  • Xinghan Chen,
  • Weifeng Huo,
  • Shuai Zhao

摘要

In this study, we designed two types of ultra-high-strength steels (UHSSs), namely, Nb-Ti and Nb-V microalloyed UHSSs, via a quenching-tempering process. Based on the microstructure and mechanical properties, the strengthening mechanisms of the steels were discussed. The results indicated that both steels achieved ultra-high tensile strength levels exceeding 2000 MPa after quenching. After tempering at 500-600 °C, a large number of martensite packets appeared, significantly reducing the strength and increasing the total elongation. The strength levels are sustained at 800-1100 MPa with the total elongation ranging from 12 to 18%. The (Nb, Ti)(C, N), (Nb, V)(C, N), and Nb(C, N) carbides formed in the Nb-Ti and Nb-V microalloyed UHSSs grow in an ordered face-centered cubic structure. The strengthening mechanisms of the two experimental steels include solution strengthening, fine grain strengthening, dislocation strengthening, and precipitation strengthening. The predominant strengthening mechanism is dislocation strengthening. Additionally, the larger precipitates in the Nb-Ti steel primarily pin dislocations at grain boundaries, contributing to grain refinement, while the finer precipitates in the Nb-V steel enhance dislocation density and precipitation hardening, leading to superior overall strength.