Theoretical Study on Impurity Distribution during Directional Solidification of Lutetium

High purity lutetium, as a rare earth metal, has important research value. In this study, the distribution of impurities Fe and Al in lutetium ingots under vacuum electron beam melting and directional solidification was analyzed through theoretical calculation. The purification effect and influencing mechanism of metal lutetium under the coupling effect of evaporation and segregation were studied. The results show that during the process of electron beam directional solidification of lutetium, although the saturated vapor pressure of impurity Al is greater than that of Fe impurity, the evaporation mass transfer coefficient of Fe is greater than that of Al. The distributions of impurity Fe and Al in metal lutetium are not only controlled by solid-liquid interface segregation, but also by gas-liquid interface evaporation. The Fe content in the area below 60% of the height of lutetium ingot decreased from 4.836×10⁻³ to 6.2×10⁻⁵, and the Al content decreased from 7.75×10⁻⁴ to 3.3×10⁻⁸, indicating a good purification effect. Temperature and solidification rate are two important parameters that affect the distribution of impurities in the process of electron beam directional solidification of lutetium. A lutetium metal ingot with high purity and uniform distribution can be obtained by reasonably adjusting the melt temperature and solidification rate.