Thermodynamic Calculations and Parameter Variations for Improving the Extraction Efficiency of Dy in Ternary Alloy System

Abstract

The extraction behavior of dysprosium (Dy) in a rapidly solidified Dy–Fe–B alloy system consisting of Dy2Fe14B and Dy6Fe23 phases was investigated using the liquid metal extraction (LME) process. Liquid magnesium (Mg) was selected as the solvent metal in LME because it forms intermetallic compounds with Dy but not with iron (Fe) and boron (B) in this process. The diffusion behavior of Dy was estimated through thermodynamic calculations and subsequently confirmed by process parameters such as temperature and reaction time. As the temperature increases, the extraction rate increases and the maximum extraction efficiency is about 74% Dy for 1 h at 1000 °C. As the reaction time increases, we achieved the maximum extraction efficiency of 95% Dy after 24 h at 900 °C. The factor affecting Dy extraction ratio up to 6 h is Dy6Fe23 phase, after which the extraction mainly occurs in Dy2Fe14B phase. Furthermore, the diffusion behavior is described in detail with analysis based on microstructural and compositional properties. The effects of process parameters on extraction rate are also discussed.