The hot tensile tests were conducted in this study to investigate the effects of Nb, B, Mo, and V on hot ductility of 25CrMo alloy steel in a temperature range of 650–850°C with strain rates of 0.005 and 0.5 s −1 . Besides, the influences of ferrite transformation and precipitates on hot ductility were also investigated by the use of SEM and TEM. Thermo-Calc and J Mat Pro were used for calculating equilibrium precipitates and CCT curves, respectively. The results indicated that the hot ductility is deteriorated with the addition of 0.04% Nb due to Nb(C,N) particles and ferrite transformation. The addition of B inhibits ferrite transformation and improves hot ductility. The hot ductility is improved with increasing strain rate from 0.005 to 0.5 s −1 due to the nucleation and growth behavior of ferrite. The fast strain rate promotes nucleation of ferrite; however, the ferrite has no sufficient time to grow up. The addition of Mo inhibits ferrite transformation and improves hot ductility. The addition of 0.12% V has no obvious effect on ferrite transformation. The hot ductility has deteriorated a little with the addition of 0.12% V due to the solution V that increases stress during hot deformation.

中文翻译：

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成分和应变速率对Cr-Mo合金钢两相区热塑性的影响

本研究中进行了热拉伸试验，以研究 Nb、B、Mo 和 V 在 650-850°C 温度范围内，应变速率为 0.005 和 0.5 s -1 时对 25CrMo 合金钢的热延展性的影响。此外，还通过使用 SEM 和 TEM 研究了铁素体转变和析出物对热延展性的影响。Thermo-Calc 和 J Mat Pro 分别用于计算平衡沉淀和 CCT 曲线。结果表明，由于 Nb(C,N) 颗粒和铁素体相变，加入 0.04% Nb 会降低热延展性。B的添加抑制铁素体相变并提高热延展性。由于铁素体的形核和生长行为，热延展性随着应变速率从 0.005 增加到 0.5 s -1 而得到改善。快速应变速率促进铁素体形核；然而，铁氧体没有足够的时间长大。Mo的添加抑制铁素体相变并提高热延展性。添加0.12% V对铁素体转变无明显影响。加入0.12%的V后，热延展性略有下降，这是由于溶液V增加了热变形过程中的应力。