Effect of Ce Substitution with La and Nd on Microstructure and Mechanical Properties of Al11Ce3

The study investigates the microstructure and mechanical properties of five cast, coarse-grained intermetallic alloys: binary Al11Ce3 and Al11La3, ternary Al11(Ce0.75La0.25)3 and Al11(Ce0.5La0.5)3, and quaternary Al11(Ce0.54La0.27Nd0.19)3 with mischmetal composition. All compounds exhibit a single phase indicating a solid solution among the rare-earth elements (RE = Ce, La, and Nd) on the Ce sublattice of Al11RE3, contrary to Thermo-Calc prediction of segregation of Ce and (La, Nd) into two insoluble compounds. The orthorhombic Immm-structured α-Al11RE3 phase’s lattice parameters increase with increasing La concentration, while the α-β phase transformation temperature decreases. The mechanical properties, encompassing high hardness (4.1–4.3 GPa), low indentation fracture toughness (0.48–0.65 MPa m1/2), together with the high twinning propensity among these five Al11RE3 compounds are remarkably similar. This similarity suggests that these Al11RE3 compounds will exhibit comparable strengthening in Al-RE-based eutectic alloys, while also positioning them as economically and environmentally favorable alternatives to the well-developed binary Al11Ce3 compound formed in current eutectic Al-Ce alloys.