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采用光学金相、硬度测量结合透射电镜观察,研究了经过弯曲或扭转变形的含铌微合金钢在等温受热时的组织稳定性问题.研究发现:弯曲与扭转变形都可以大幅度提高微合金钢的硬度;在随后的550℃等温受热过程中,弯曲变形区的硬度迅速下降,同时伴随贝氏体向平衡组织的演变;而扭转区在等温过程中的硬度始终高于未变形区,同时钢中贝氏体组织基本得以保持.扭转应变量越大,硬化效果越强,并且在随后的等温受热过程中能保持这种硬度上的优势.弯曲与扭转变形均导致贝氏体板条内位错密度显著增加.弯曲变形区的位错分布不均匀,其中的低位错密度区易于在随后的等温受热过程中演变为平衡组织多边形铁素体的形核核心;而扭转变形区内位错分布均匀,并且在随后的等温受热过程中位错分布不发生显著改变.这些结果表明,不同的冷变形方式对微合金钢中贝氏体热稳定性的影响存在显著差异.
Using optical metallography, hardness measurement combined with transmission electron microscopy, we studied the microstructure stability of microalloyed niobium-containing microalloyed steel subjected to isothermal heating after bending or torsion deformation.The results show that both bending and torsional deformation can greatly improve microalloyed steel The hardness of the bending deformation zone decreased rapidly with the accompanying bainite evolution to the equilibrium structure. However, the hardness of the torsional zone in the isothermal process was always higher than that in the undeformed zone, and the steel Bainite in the basic to maintain the larger torsional strain, the harder the stronger, and in the subsequent isothermal heating process to maintain the hardness of the advantages of both bending and torsional deformation lead to bainite lath internal position The density of dislocations in the bending deformation zone is not uniform, and the low dislocation density zone is easy to evolve into the nucleation center of the equiaxed polygonal ferrite during the subsequent isothermal heating. The dislocation distribution in the deformation zone Uniform, and the dislocation distribution does not change significantly during the subsequent isothermal heating.These results show that different cold deformation methods for micro-alloy steel Bayesian There were significant differences in the thermal stability.