锰溶质原子与钛、锆氧化物之间的相互作用及其对晶内铁素体形核的影响

Intragranular ferrite is not only utilized in the microstructure and strength-toughness control in the welds and welding heat affected zone of high strength low alloy steel，but also gradually utilized in the refinement of matrix microstructure of the high strength low alloy steel. However, there is no universal agreement on the nucleation mechanisms of intragranular ferrite on the non-metallic inclusions. In view of the phenomenon that the intragranular ferrite can be nucleated at the oxides of titanium and zirconium in the steels containing manganese, in order to explore the interaction mechanisms between manganese solute atom and the oxides of titanium and zirconium during heat treatment and the effect of the interaction result on the intragranular ferrite nucleation, this proposal intends to study the potency and efficiency of oxides of titanium and zirconium in promoting the intragranular ferrite nucleation by means of dual solid-state pressure bonding experiment, detect the profiles of the solute atoms adjacent to the oxides/steel interface by means of electron probe micro-analyzer (EPMA), and study the thermodynamic mechanism of manganese solute atom migrating into the cation vacancy in the oxides by means of first principle calculation. Meanwhile, the potency and efficiency of the oxides of titanium and zirconium in promoting the intragranular ferrite nucleation will be qualitatively evaluated. The research results can not only be utilized to guide the effective control of the intragraluar ferrite formation in the titanium and/or zirconium killed steels, but also enrich the fundamental research on the nucleation mechanism of the intragranular ferrite. The current proposal exhibits important significance in terms of industrial applications and scientific researches.

晶内铁素体不仅可用于低合金高强度钢焊缝和焊接热影响区的组织与强韧性控制，也逐渐地用于细化低合金高强度钢的基体组织，但非金属夹杂物促进晶内铁素体形核的机制尚无统一认识。本申请项目针对含锰钢中钛、锆氧化物可有效促进晶内铁素体形核的这一重要现象，采用双重热压连接实验对比研究钢中钛、锆氧化物促进晶内铁素体形核的能力和效率，采用电子探针微区分析仪(EPMA)检测分析热压连接实验后氧化物/基体钢附近溶质原子浓度分布，采用第一性原理方法研究钢中锰溶质原子进入氧化物中阳离子空位的热力学机制等，以揭示热处理过程中锰溶质原子与钛、锆氧化物之间的相互作用机制以及相互作用结果对晶内铁素体形核的影响，并对钛、锆氧化物促进晶内铁素体形核的能力和效率进行定性评价。此研究成果既可指导钛、锆脱氧钢中如何有效控制晶内铁素体的形成，又可丰富晶内铁素体的形核机理研究，具有重要的工业应用和科学价值。

钢中的溶质原子如Mn和C等可能和钢中钛、锆氧化物等发生相互作用，某些氧化物周围可形成奥氏体稳定化溶质原子贫乏区，从而提高了夹杂物附近奥氏体向铁素体转变的相变驱动力，即促进了铁素体的形核而细化了组织从而提高了材料的综合力学性能。本项目通过第一性原理计算、双重热压连接实验和电子探针分析等对含锰钢中钛、锆和铝氧化物促进铁素体形核的能力、机制和效率进行了较为完整的实验和理论分析。研究发现：在本项目设计的含锰钢中氧化物促进铁素体形核的能力按照TiO2 (ZrO2), Ti2O3 (Ti3O5), Al2O3 和TiO顺序递减；该实验结果与采用计算锰溶质原子在钢基体和氧化物中的分配焓的第一性原理计算结果基本相符。本项目还对比研究了铝脱氧和钛、锆复合脱氧生产的工业用钢的组织特征和力学性能，结果发现钛、锆复合脱氧不但可以细化钢中夹杂物，在奥氏体-铁素体固态相变过程中又可作为铁素体的形核质点，其可明显提高材料的综合力学性能；同时采用高温激光扫描共聚焦显微镜对钛锆复合氧化物促进铁素体形核的能力进行了原位观察的验证。本项目研究成果不仅可对钛、锆复合脱氧钢中钛、锆等氧化物对夹杂物和组织的细化提供实验和理论支撑，而且也可为研究其他复合夹杂物，例如稀土氧化物夹杂等促进铁素体形核的能力和机制研究提供实验和理论计算方法借鉴。