镁熔体中富Fe团簇演变与Al–Fe分离机制的研究

The recycling of high Fe–contained Al–Si alloys is a green industry which is suited to the sustainable development of aluminum materials. Eliminating the harmful effect of Fe, achieving the separation of Al–Fe is one of the key problems. Different from traditional methods for iron–removal, a novel method using magnesium melt to realize Al–Fe separation is proposed in this project. By adjusting the evolution procedure of Fe–rich clusters in the melt, the Fe–rich phases are designed to transform to Al0.7Fe3Si0.3 during the solidification process. The compositional and structural evolution behaviors of Fe–rich phase in Mg melt will be systematically studied using a series of structural analysis means, such as the Liquid Metal X–ray Diffractometer (LMXRD) and so on. The correlation between liquid structure and the evolution process will be studied, and the reaction thermodynamics and critical reaction conditions will be analyzed. The effecting mechanism of Si in the evolution process from Fe–rich phase to Al0.7Fe3Si0.3 and in the Al–Fe separation process will be revealed, aiming at providing theoretic support for achieving Mg–Al–Si alloy and Fe–Mg alloy which can be used as nodulizer in cast iron industry. This project may also be referred by relative study about the evolution of other transition metal clusters in Mg melt.

高Fe含量铝硅合金的回收再利用是适应铝资源可持续发展的绿色产业，消除Fe元素的有害作用，对其进行“Al–Fe分离”是该过程的关键问题之一。不同于传统的除Fe手段，本项目提出了一种利用镁熔体来实现“Al–Fe分离”的新方法：通过调控富Fe团簇演变，促进镁熔体冷凝过程中富Fe相向Al0.7Fe3Si0.3转变，借助液态金属X射线衍射仪等系列结构分析手段系统地研究富Fe相组分、结构的演变行为。研究镁熔体结构与富Fe相析出、演变过程的相关性；分析富Fe相的反应热力学和临界形成条件；探明Si原子在“富Fe相→Al0.7Fe3Si0.3相”转变与“Al–Fe分离”中的作用机制，为获得Mg–Al–Si系中间合金与可用作铸铁球化剂的Fe–Mg系中间合金提供理论支持。本项目也为镁熔体中其它过渡族金属团簇的演变及析出研究提供参考和依据。

铝合金回收再利用是铝产业未来的发展趋势。高Fe含量的Al-Si-Fe合金由于形成了富Al的金属间化合物，导致此部分Al难以被有效回收。因此，本项目提出了一种利用镁熔体来实现“Al–Fe分离”的新方法：将Al-Si-Fe合金引入到Mg熔体中，通过调控β–Al5FeSi和γ–Al3.5SiFe等高Al含量富Fe相的演变行为，以获得“富Fe乏Al”的Al0.7Fe3Si0.3相。基于实验与计算研究，研究者发现：通过对比β–Al5FeSi与Al3Fe相结构、成分、形貌在Mg熔体中的演变规律，证实了主导原子Si的扩散是导致富Fe相演变的关键因素；由于Al0.7Fe3Si0.3为亚稳相，其在熔体冷凝过程中会向Al5Fe2、Al13Fe4等相发生演变，高的熔炼温度与快的冷却速度更有利于“Al-Fe分离”效果的提升；通过调控富Fe相的沉降过程，可在熔体下层得到Mg-Fe系合金，将Mg-Fe合金应用于球墨铸铁的球化处理，可有效实现石墨球的细化；通过设计熔体分离工艺与装置，将Al-Si-Fe合金一分为二，上层的Mg-Al-Si合金可在工业获得应用，下层的Mg-Fe合金可作为新型球化剂使用，从而实现了Al-Si-Fe合金的回收再利用。本项目的相关成果不仅为镁熔体中其它过渡族金属团簇的演变及析出研究提供了参考，也为新型Mg基复合材料的设计与开发提供了新思路，具有重要的现实意义和科学价值。