基于密度泛函理论和分子动力学含稀土夹杂物/渣系的相结构与溶液模型研究

The results are always favorable when rare earth (RE) elements are employed into the steel or slag . However, the research and application process of RE in steel production are limited as the basic thermodynamic data of oxides systems containing RE is very scarce. In this work, multi-technique experiments accompanying calculations are employed to study the structures and thermodynamics of intermediate compounds, solid solutions and high temperature melts in the Al2O3-SiO2-RE2O3(RE=La，Ce) system, which is the common composition of complex non-metallic inclusions and metallurgical slag. The ab-initio molecular dynamics based on density functional theory are first introduced to study the complex oxides system. The quantitative effect and mechanism of rare earth and aluminum elements on the silicate structures are revealed from the electronic structures. Then a thermodynamic solution model, which takes the phase structure parameters expressed from intra-particle properties including electron spin angular momentum and magnetic moment as equilibrium criterion, will be built. And Finally, the phase diagrams of Al2O3-SiO2-RE2O3 systems including each binary systems and isothermal sections are given and the thermodynamic database of excess Gibbs free energy optimized from modified quasi-chemical solution and double sublattice solution model by CALPHAD technique is created. The research results will play a fundamental role in the application of rare earth elements to special steel production, metallurgical slag development and so on.

稀土在特种钢的开发、冶金渣的设计方面均取得了良好的效果，然而含稀土氧化物多元体系的基础热力学数据十分匮乏，限制了稀土在钢铁生产过程中的应用与研究进程。基于此，本项目选择含稀土复杂夹杂物、冶金渣中共有的Al2O3-SiO2-RE2O3(RE=La，Ce)体系为研究对象，结合多种实验方法与计算并行的手段对其中间化合物、固溶体相、高温熔体相的结构及其热力学性质展开研究。将基于密度泛函理论的分子动力学引入至复杂氧化物体系的研究，从电子尺度揭示稀土、铝元素对硅酸盐网络结构的定量作用规律，构建以基于粒子内禀性质（电子自旋角动量、磁矩等）的相结构参数为平衡判据的溶液模型，并结合CALPHAD技术绘制系统、准确的此三元系相图（含各二元系相图与等温截面图）并创建基于修正的准化学溶液和双亚点阵溶液模型的超额吉布斯自由能数据库。研究结果将为稀土资源在钢种开发、冶金渣设计等方向的应用提供理论依据和数据支撑。

稀土在特种钢的开发、冶金渣的设计方面均取得了良好的效果，然而含稀土氧化物多元体系的基础热力学数据十分匮乏，限制了稀土在钢铁生产过程中的应用与研究进程。基于此，本项目以Al2O3-SiO2-RE2O3(RE=La，Ce)体系为研究对象，结合多种实验方法与计算并行的手段对其中间化合物、硅酸盐相结构及其热力学性质展开研究。得出了铝元素对硅酸盐结构的影响作用规律、混溶间隙区的形成机制，厘清了三元系及相关二元系稳定存在的中间化合物，绘制了各二元系相图并扩展得到三元系相图及其相关热力学数据库，总结形成了相图绘制的思维导图。根据得到的热力学数据与实验结果，建立了更为全面的稀土夹杂物析出耦合热力学模型，并应用于稀土耐热钢的夹杂物变质过程与机理阐释，取得了理想的效果。研究成果将为材料基因组开发、稀土资源在钢种开发、冶金渣设计、热力学软件开发等方向的应用提供理论依据和数据支撑。