3D characteristics of Fe-rich phase and its effect on mechanical properties of AA3104 alloys

Scrap cans have significant recycling potential, but the microstructure and properties of recycled aluminum are compromised by the impurities. The impact of Fe content on the microstructure and mechanical properties of AA3104 alloy was studied by scanning electron microscopy (SEM), synchrotron radiation X-ray computed tomography (SRXCT), universal tensile testing, and thermodynamic calculations. The results showed that as Fe content increased, the Fe-rich phase transitioned from α-Al15(Mn,Fe)3Si2 to Al6(Mn,Fe). The SEM morphology changed from Chinese-script to fish-bone and fine-granular structures. Moreover, both the total area fraction of Fe-rich phase and average area of individual Fe-rich phases increased with Fe content, while the average area of individual Fe-rich phases decreased when the Fe content exceeded 0.35%. Deep-etched and SRXCT results show that the 3D morphology of the Fe-rich phase changed from a coral-like structure, consisting of multibranch interconnections by flakes, to a rod-like structure with high connectivity, where independent rods interconnected by the α-Al matrix. Furthermore, at higher Fe contents, the Fe-rich phase shows increased thickness and a more compact 3D morphology. Increasing Fe content decreased the ductility of the alloys, but has no significant change when Fe content exceeded 0.35%. This paper expands the range of Fe content for the application of recycled AA3104 alloy.