A eutectoid phase transformation for the primary intermetallic particle from Alm(Fe,Mn) to Al3(Fe,Mn) in AA5182 alloy Original Research Article

The size and morphology evolution of the primary intermetallic particles in a DC-cast AA5182 alloy during homogenization at 470 and 520 °C has been studied. A eutectoid phase transformation of the primary particles Alm(Fe,Mn) → Al3(Fe,Mn) + Al is observed by field emission gun scanning electron microscopy (FEG-SEM) and transmission electron microscopy (TEM). After the transformation, Alm(Fe,Mn) particles become a lamellar mixture of Al3(Fe,Mn) and Al, which is believed to be beneficial to the break-up of the large primary particles during hot rolling. The transformation mechanism and the transformation kinetics have been studied. During isothermal treatment at 520 °C, the fractional transformation rate is mainly controlled by nucleation. At 470 °C, the phase transformation is controlled by both nucleation and growth of Al3(Fe,Mn) in Alm(Fe,Mn) phase.