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<p>In low-carbon vanadium microalloyed steels, the complex microalloying elements can alter the behavior and kinetics of the vanadium precipitation. In the present study, the effect of Mo and Nb addition on the precipitation behavior and kinetics of nanometer-sized VC and VCN precipitates were investigated during isothermal treatment. In this respect, isothermal heat treatments at different temperatures (600–750&#xa0;°C) and holding times (20–3600&#xa0;s) executed for V–Nb–Mo, V–Nb, V–Mo, and V steels. The kinetics and isothermal precipitation behavior of VC and VCN were examined by using transmission electron microscopy and tensile deformation. Results showed that most of the vanadium precipitates are interphase and random carbides developed in the ferrite matrix. As the isothermal holding time increases, precipitation takes place in five distinct phases: (i) nucleation period, (ii) the early stage of precipitation, (iii) active growth period, (iv) nearly steady state, and the (v) coarsening period. The Mo and Nb enhance the nucleation sites for V precipitation and also slow down the migrating interphase boundaries. The maximum precipitation strengthening was observed in V–Nb–Mo steel that mainly attributed to the existence of higher amount of nanometer-sized interphase precipitates. The synergistic effects of Mo and Nb govern the nucleation and development of VC precipitates, leading to a fine and even distribution of nanoscale precipitates.</p>

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The Influence of Molybdenum and Niobium on the Vanadium Precipitation Behavior in Low-Carbon Micro-alloyed Steels During Isothermal Heat Treatment

  • 期刊论文

  • 发表日期：

    2025年10月27日

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  • Sayed Ghafar Hashemi,
  • Mehdi Shaban Ghazani,
  • Beitallah Eghbali

摘要

In low-carbon vanadium microalloyed steels, the complex microalloying elements can alter the behavior and kinetics of the vanadium precipitation. In the present study, the effect of Mo and Nb addition on the precipitation behavior and kinetics of nanometer-sized VC and VCN precipitates were investigated during isothermal treatment. In this respect, isothermal heat treatments at different temperatures (600–750 °C) and holding times (20–3600 s) executed for V–Nb–Mo, V–Nb, V–Mo, and V steels. The kinetics and isothermal precipitation behavior of VC and VCN were examined by using transmission electron microscopy and tensile deformation. Results showed that most of the vanadium precipitates are interphase and random carbides developed in the ferrite matrix. As the isothermal holding time increases, precipitation takes place in five distinct phases: (i) nucleation period, (ii) the early stage of precipitation, (iii) active growth period, (iv) nearly steady state, and the (v) coarsening period. The Mo and Nb enhance the nucleation sites for V precipitation and also slow down the migrating interphase boundaries. The maximum precipitation strengthening was observed in V–Nb–Mo steel that mainly attributed to the existence of higher amount of nanometer-sized interphase precipitates. The synergistic effects of Mo and Nb govern the nucleation and development of VC precipitates, leading to a fine and even distribution of nanoscale precipitates.