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

该项目旨在探索一种合成纯金属的替代方法。核心元素是分离结晶，这将通过一个内部冷却的旋转结晶器(简称“冷却手指”)进行，从受污染的熔体中生长出的超纯金属在上面生长。在成功的情况下，这种方法有可能取代目前的区域熔化过程。然而，目前对这一方法的有效应用，特别是对过程控制参数以及对过程中的机理的描述缺乏了解。通过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，定量地描述了渐进相界的分相过程，并与工艺参数进行了关联。对铝进行了能源部支持的大量实验研究，以验证和验证数值预测。这里选择铝作为模型金属，是因为存在模拟所需的热力学和物理数据，从而能够定量研究冷指方法的基本原理和主要工艺参数。铝在各种纯度方面都具有成本效益，这意味着研究成本显著降低。该项目的结果是针对有效清洁的工艺窗口以及控制凝固前沿动力学的相关参数和工艺模型。具有不同研究兴趣的三个工作组的合作旨在提供对这一迄今未探索的结晶过程的潜力的定量了解。基于物理的模拟模型将有助于简化向其他合金化系统的转移。

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.