高硼铸钢/铝液界面反应生成周期性层片结构的机理研究

The periodic layered structure (PLS) formed during the interfacial reaction was a kind of complex in-situ self-organized structure. However, the materials systems of formation of PLS were still not mature, the formation mechanism of this structure was still in dispute, and there was almost few report on the application of it. According to the different interfacial behaviors of Fe2B which played a key role in improving the corrosion and corrosion-wear resistance of Fe-B cast steel in molten zinc and molten aluminum, respectively, the PLS would form at the Fe2B/Al interface, and the content of Cr in Fe-B cast steel had a great influence on the formation of PLS. Focused on the three major issues (such as the effect of Cr on the PLS and its mechanism) put forwarded in this study, the interfacial reaction between Fe2B and molten aluminum and the evolution of interfacial microstructures were investigated by adjusting the content of Cr contained in Fe-B cast steel, the parameters of immersion test in molten aluminum and diffusion annealing method, in order to explore the reaction process and formation mechanism of PLS. Not only these results would be a supplement for the key scientific problems and the common law in the PLS, but also extend the materials system of PLS and the phase diagram of Fe-Cr-B-Al-Zn, and be helpful for the wide application of Fe-B cast steel as a kind of structural functional materials in the field of corrosion and corrosion-wear in high temperature molten metal (such as zinc and aluminum).

界面反应生成的周期性层片结构（PLS）是一类非常复杂的原位自组织结构，其形成体系还未完善，生成机理还存在争议，应用价值也鲜有讨论。本项目基于对高硼铸钢耐锌、铝液腐蚀及腐蚀-磨损性能起关键作用的Fe2B在锌、铝液中的不同界面行为，其中，在铝液中会与铝液发生化学反应并在固-液界面上生成PLS，Cr元素的含量对PLS的生成有着至关重要的影响，重点围绕提出的诸如Cr对PLS的影响及其机理等三大问题并通过调整Cr含量、铝液浸入试验参数及扩散退火等方法来系统研究高硼铸钢中的Fe2B与铝液之间的化学反应及界面组织结构的演变，探索该反应生成PLS的反应过程及其机理。项目研究成果对阐明PLS的形成机理，揭示其共性规律，拓展其材料体系及Fe-Cr-B-Al-Zn多元相图等方面具有重要意义，并将推动高硼铸钢作为一种结构-功能材料在耐高温金属（锌、铝）熔体腐蚀-磨损等特殊领域获得广泛应用。

界面反应生成的周期性层片结构（PLSs）完全区别于层片状共晶组织，其只存在于少数特殊的材料体系中。项目在前期研究Fe-Cr-B铸钢Al液腐蚀时偶然发现其组织中的硼化物与Al液界面反应生成PLSs的基础上，采用调整Fe-Cr-B铸钢中的Cr含量、Al液中的Zn含量及扩散退火，并结合三维原子探针层析技术及X射线同步辐射试验等手段揭示了Fe-Cr-B铸钢与Al液界面反应生成PLSs的机理：Fe-Cr-B铸钢中的Cr含量对PLSs的生成起着关键作用，只有Cr含量位于一定区间内才会生成PLSs；与Al液界面反应生成PLSs的硼化物为(Cr,Fe)2B；PLS由Cr-Al-B金属间化合物（IMC）和Fe-Al IMC交替组成。Al液中Zn含量对(Cr,Fe)2B/Al液界面反应生成PLSs有着复杂影响，Fe-Cr-B铸钢中的Cr含量越高，其与Al-Zn熔体界面反应生成PLSs时的Zn含量也越大；可根据(Cr,Fe)2B/Al-Zn熔体界面反应是否生成PLSs来判断Fe/Al界面反应向Fe/Zn的临界转变。扩散退火过程仍然可以生成PLSs。总体来说，(Cr,Fe)2B/Al界面反应生成PLSs符合扩散应力理论。然而，在PLS形成的初始阶段，交替层并非同时形成，首先发生的Fe原子从(Cr,Fe)2B相的优先溶解及其与向内扩散的Al原子反应生成Cr-Al-B IMC。另外，该机理还难以解释热浸镀铝及扩散退火过程中PLSs形貌上的差异。项目顺利完成了研究计划的相关研究内容并达到预期目标，还拓展研究了PLSs在NaCl溶液中的腐蚀行为，并获得国家自然科学基金地区基金和海南省自然科学基金高层次人才项目的立项资助，相关研究成果有望促进PLSs在海洋防腐领域的重要应用，并为我国实现海洋强国和海南省自贸港建设的防腐材料设计提供理论指导。