Microstructure and property optimization of Al–8Ce alloys: Electromagnetic stirring and Sc–Zr microalloying

To further improve the strength of an Al–Ce alloy, the effects of electromagnetic stirring treatment, Sc–Zr microalloying, and their compound action on the microstructure and properties of the Al–8Ce alloy were investigated for the first time in this study. The results show that the primary α-Al becomes coarse, the eutectic Al11Ce3 phase is refined and the lamellar spacing increases significantly due to the combined effect of forced convection of electromagnetic field and dendrite fragmentation and nucleation in Al–8Ce alloy after electromagnetic stirring treatment. After the Sc–Zr microalloying treatment of the Al–8Ce alloy, the α-Al changes from a dendritic to fine round morphology, and the eutectic Al11Ce3 phase changes from lamellar to fibrous, which is due to the heterogeneous nucleation of Al3(Sc, Zr) phase and the adsorption refinement caused by the enrichment of Sc and Zr. The optimization effect of Sc–Zr microalloying on the mechanical properties of the Al–8Ce alloy was better than that of electromagnetic stirring and their synergistic treatment. The tensile strength and yield strength of Al–8Ce alloy with Sc–Zr additions were increased from 157 MPa to 85 MPa–192 MPa and 115 MPa, respectively, by 22.3 % and 35.3 %. After aging treatment, the tensile strength (from 192 to 272 MPa) and yield strength (from 115 to 221 MPa) significantly improved owing to the secondary precipitation of Al3(Sc, Zr) particles. The precipitation strengthening of the Al3(Sc, Zr) phase was the main contributor to the high yield strength of the alloy.