Mechanisms and Process Model of Ultra-Refining of Metals by Crystallization via a rotating cooled cylinder

该项目旨在探索合成纯金属的替代方法。核心要素是分步结晶，其通过内部冷却的旋转结晶器（简称为“冷却指”）进行，来自受污染熔体的超纯金属在其上生长。这种方法在成功的情况下有可能取代目前的区域熔化工艺。然而，这种方法的有效应用的理解，特别是过程控制参数以及在该过程中的机制的描述，目前缺乏。通过在宏观过程和微观组织尺度上的热物理计算和凝固模拟的相互作用，在渐进相边界处的分层过程将被定量地描述并与过程参数相关联。对铝进行了广泛的能源部支持的实验研究，以验证和确认数值预测。由于模拟所需的热力学和物理数据的存在，允许定量研究冷指法的基本原理和主要工艺参数，因此选择铝作为模型金属。铝在各种纯度下都具有成本效益，这意味着研究成本的显着降低。该项目的结果是针对有效的清洗和相关的参数和工艺模型，用于控制凝固前沿动态的工艺窗口。具有不同研究兴趣的三个工作组的合作旨在对这一迄今尚未探索的结晶过程的潜力提供定量的了解。基于物理的模拟模型将有助于简化转移到其他合金系统。

The project aims to explore an alternative method for the synthesis of pure metals. The core element is fractional crystallization, which is to be conducted through an internally cooled rotating crystallizer (in short named "cooled finger"), on which the ultra-pure metal from a contaminated melt grows. This method has in the case of success the potential to replace the current zone melting process. However, the understanding of an effective application of this method, particularly the process controlling parameters as well as a description of the mechanisms in the process, is currently lacking. By interplay of thermophysical computations and solidification simulation on a macroscopic process and microscopic microstructure scale, the demixing processes at the progressive phase boundary are to be quantitatively described and correlated with process parameters. Extensive DoE-supported experimental investigations to verify and validate numerical predictions are performed on aluminum. Aluminum has been chosen here as the model metal due to the existance of the required thermodynamic and physical data for the simulation that allowing a quantitative study of the fundamental principles and dominant process parameters for the cold finger method. Aluminum is cost-effective in various purities, which means a significant reduction in research costs. The project results are aimed at process windows for efficient cleaning and the associated parameters and process models for controlling the solidification front dynamics. The cooperation of three working groups with different research interests aims to provide a quantitative understanding of the potential of this - so far - unexplored crystallization process. The physically-based simulation model will facilitate simplified transfer to other alloying systems.