Abstract Hot-deformation can refine grain size and change the dynamics of austenite-ferrite phase transformation during thermo-mechanical processing of microalloyed steels. Here, atom probe tomography has been used to characterize nanoscale precipitates and segregation in Ti-Mo microalloyed steels processed with and without hot-deformation at 890 °C. It provides a comprehensive understanding of solute redistribution in both the grain interior and grain boundary regions. The results show that coarse (Ti, Mo)C precipitates are formed at grain boundaries, whereas fine precipitates are densely distributed in grain interiors, regardless of deformation conditions. Precipitate-free zones are developed near grain boundaries in the undeformed Ti-Mo steel, but absent in the hot-deformed steel. The elimination of precipitate-free zone in the hot-deformed steel is attributed to the high dislocation density and accelerated γ → α transformation caused by hot-deformation. The majority of Ti, Mo, and C atoms partition into (Ti, Mo)C precipitates, but Mn, Si, and Al atoms are mainly in solute state in ferrite matrix and segregation at grain boundaries. The hot-deformation significantly changes the C segregation at grain boundaries, but has little effect on other solute elements.

中文翻译：

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热变形对Ti-Mo微合金钢晶界析出和偏析的影响

摘要 在微合金钢的热机械加工过程中，热变形可以细化晶粒尺寸并改变奥氏体-铁素体相变的动力学。在这里，原子探针断层扫描已被用于表征在 890 °C 下经过和不经过热变形处理的 Ti-Mo 微合金钢中的纳米级沉淀和偏析。它提供了对晶粒内部和晶界区域中溶质再分布的全面了解。结果表明，无论变形条件如何，在晶界处形成粗的(Ti，Mo)C析出物，而细的析出物密集地分布在晶粒内部。在未变形的 Ti-Mo 钢中，在晶界附近形成无沉淀区，但在热变形钢中不存在。热变形钢中无析出区的消除是由于热变形引起的高位错密度和加速的γ→α转变。大多数 Ti、Mo 和 C 原子分配成 (Ti, Mo)C 析出物，但 Mn、Si 和 Al 原子主要以溶质状态存在于铁素体基体中并在晶界偏析。热变形显着改变了晶界处的 C 偏析，但对其他溶质元素影响不大。