LAUSR

Abstract The effects of Mg additions on the Fe-containing intermetallic compounds and the heterogeneous nucleation of α-Al were investigated in Al-1.4Fe-0.7Mn-xMg alloys using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experimental results show that the morphology of Al6(Fe,Mn) in eutectic structure was significantly modified from needle-like to plate-like and then Chinese Script with increasing Mg concentration. The effects of Mg addition on the composition and crystal structure of Al6(Fe,Mn) were also investigated. No Mg was detected in the Al6(Fe,Mn) compounds. However, clear interfacial segregation of Mg on the surface of the Al6(Fe,Mn) particles was observed. The grains of α-Al were refined with increased Mg addition. It is also found that the Mg addition in the Al alloys resulted in change to the major naturally formed oxides from Al2O3 to MgAl2O4, and eventually changed the heterogeneous nucleation of α-Al. The direct evidence of heterogeneous nucleation of α-Al on the naturally formed MgAl2O4 particles was observed.