Aluminothermic Reduction of Lanthanum Oxide

Abstract Rare earth elements (REEs) are promising alloying elements for enhancing aluminum properties; among them is lanthanum (La). In addition, a new family of Al–La(Ce) casting alloys is under development, exhibiting excellent property retention at elevated temperatures. Traditionally, LM–RE (light metal–rare earth) alloys are produced by directly adding pure RE metals to molten Al. An alternative and potentially more cost-effective method is by direct metallothermic reduction of RE oxides using Al as the reductant. In this study, the reactions between Al and La 2 O 3 were studied through a systematic investigation of microstructural evolution combined with differential scanning calorimetry (DSC) measurement. The results for macro-samples show that Al and La 2 O 3 reactions are rapid. For a mixture containing Al–10 wt pct La 2 O 3 , the reaction proceeds quickly, reaching completion within approximately 15 minutes. The final reaction products consist of a mixture of Al, Al 2 O 3 , and Al 11 La 3 . The details of the reaction mechanism were studied using DSC for Al–50 wt pct La 2 O 3 mixtures. The reaction mechanism follows a complex multi-step pathway in which La 2 O 3 sequentially transforms into Al 7 La 33 O 60 , AlLaO 3 , and Al 11 LaO 18 . The kinetic analysis results suggest that the reaction is diffusion-limited. The study demonstrates the potential of metallothermic reduction as a viable route for producing Al–RE alloys.