A novel modifier Al-Sr-RE for improving the microstructure and mechanical properties of recycled AA3104 alloy

The microstructure and properties of recycled AA3104 alloy are affected by impurities, such as Fe and Si. In this paper, Al-Sr-RE is proposed to improve the microstructure and mechanical properties of the AA3104 alloy with high Fe content. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermodynamic calculation, and synchrotron radiation tomography (SRXCT) are employed to investigate the morphological characteristics, solidification path of Fe-rich phases. The results showed that adding trace Sr or Ce on the basis of Al-5Ti-1B does not lead to a significant change in grain, while trace Al-8Sr-8Ce alone had no obvious refinement on α-Al. But the Al-8Sr-8Ce change the 2D morphology of the Fe-rich phases from the Chinese-script to the skeletal-like and short rod-like, and the 3D morphology from a plate-like branched structure to a rod-like branched structure. The average equivalent diameter of the Fe-rich phases decreased 12.16% compared to the Al-Ti-B alloy, and the average sphericity increased by 5.00%. Adding trace Sr or Ce on the basis of Al-5Ti-1B, as well as Al-8Sr-8Ce, promoted the mechanical properties of the alloy. Especially, the Al-Sr-Ce alloy presented the optimum mechanical properties, its tensile strength, yield strength and elongation increased 7.77%, 10.87% and 24.06%, respectively. This paper provided a new modifier for Fe-rich phase modification of recycled Al-Mn-Mg alloy with high Fe content.