Recently, alloys such as Al-Sc and Al-Mg-Sc came to the forefront due to the reinforcement effect of scandium on the properties of aluminum such as mechanical strength, thermal stability, resistance to recrystallization, resistance to intergranular fracture and corrosion [1]. The main scandium source for these aluminum alloys is the Sc₂O₃ by-product obtained during uranium (U), tungsten (W) or tantalum (Ta) production. It has been shown that it is possible to produce Sc by the molten salt electrolysis method with dissolution of Sc₂O₃ in Na₃ScF₆ as in the Hall-Héroult process [2]. This scandium can be used to produce Al-Sc alloy in-situ, provided that required amount of aluminum was already present in the reactor. Furthermore, the production of Al-Sc alloy by the dissolution of Sc₂O₃ in a molten salt containing CaCl₂, in which the solubility of oxide ions is very large has been reported [3]. The Al-Sc alloy formation by the reduction of other Sc containing compounds in a molten salt containing CaCl₂ was investigated in this study. The preliminary tests revealed that Al₃Sc intermetallic was successfully formed and distributed homogeneously throughout the Al matrix as confirmed by the XRD, SEM-EDS and optical microscopy analyses. As can be seen in the optical micrograph shown in Figure (a), due to the long electrolysis and the high voltage applied, calcium contamination was observed by the presence of black Al₄Ca eutectics in between the white faceted Al₃Sc intermetallics. On the other hand, in the optical micrograph shown in Figure (b), it can be seen that the calcium contamination was inhibited by changing the electrolysis duration and the voltage while keeping the homogeneous distribution of Al₃Sc.

References

[1]Ahmad, Z. (2003). The properties and application of scandium-reinforced aluminum. JOM, 55(2), 35-39.

[2] Vickery,R.C. Production of scandium and yttrium. U.S. Patent No 3,111,467, 1963

[3] Harata, M., Yasuda, K., Yakushiji, H., & Okabe, T. H. (2009). Electrochemical production of Al–Sc alloy in CaCl2–Sc2O3 molten salt. Journal of Alloys and Compounds, 474(1), 124-130.