Effect of cooling rate on AlFe primary and eutectic phase growth evolution in an Al-2Fe-1Mn alloy

A higher percentage of recycled Al often increases Fe content, promoting the formation of Fe-rich intermetallic phases with morphologies that detrimentally affect the alloy's mechanical properties. Nevertheless, there is a scarcity of research focusing on the impacts of cooling rate in the microstructural morphology in alloys containing Mn. This study aims to characterize the AlFe and Al(Fe,Mn) phases formed during the solidification of the Al-2 wt% Fe-1 wt% Mn alloy for samples at 1 K/s and 3 K/s. The methodology includes traditional 2D techniques, such as metallography, SEM-EDS, and EBSD, with non-destructive 3D X-ray Computed Tomography (XCT) analysis to evaluate the complex morphologies of the formed intermetallic phases. The presence of primary star-like Al13Fe4 and trefoil-like Al6(Fe,Mn) phase morphologies was observed in both 1 K/s and 3 K/s samples. The presence of Mn as an alloying element, combined with relatively increased cooling rates, reduces the fraction of primary phases, particularly the star-like phase at 3 K/s. Moreover, the formation of the Al6(Fe, Mn) phase as part of the eutectic microconstituent with the Al phase was favored, transitioning from a divorced morphology to eutectic colonies with increasing cooling rate. •The morphologies star-like (Al13Fe4) and trefoil-like (Al6(Fe, Mn)) were observed.•The presence of Mn with an increase in the cooling rate favored the stabilization of Al6(Fe, Mn).•Al6(Fe, Mn) primary phase showed greater alignment with the solidification direction.•Eutectic’s nature was altered from divorced to coupled growth with an increase in the cooling rate.