Experimental and Numerical Investigation of a Solidification-Based Aluminum-Cooled Finger Refinement Process From Micro to Macro-Scale

Abstract The interest in ultra-pure metals is steadily growing due to the increasing demand for these materials in modern technology. To be able to meet the increasing demand in the future, it is necessary to implement more efficient and productive processes. As a fractional crystallization method in this application area, the cooled finger method exhibits higher productivity and lower energy requirements when compared to industry well-established methods like zone melting. In this study, the mechanisms and relevant phenomena crucial for a successful implementation of a cooled finger process were investigated using a multidisciplinary approach. With carefully selected process parameters, we present here an experimental setup with a purification potential of approximately 80 pct. Additional micro- and macro-scale simulations demonstrate that the process is sensitive to parameters such as rotation rate, cooling rate, and temperature gradient within the melt, which explains the difficulty in optimizing this process in practice. An analysis and description of various phenomena that characterize the behavior of the cooled finger process are presented within this multi-scale approach. As a result, these approaches can also be transferred to the description of processes for other metals, opening application areas outside of the purification of aluminum.