Transformation of the metastable Al6 Fe intermetallic phase during homogenization of a binary Al-Fe alloy

Abstract

Within the scope of this research the transformation of the Al6 Fe metastable phase was analyzed via Differential Scanning Calorimetry (DSC), optical and Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). A binary Al-Fe1.1 low-impurity alloy was produced with refined raw materials in a controlled environment. With a cooling rate of 35 K/s, solidification of the Al6 Fe metastable phase was achieved. The samples were homogenized at 600◦ C for 2–24 h. Results of a qualitative analysis of metallographic samples show that the transformation began on grain boundaries, forming an Fe-phase free region, but after 2 h began to take place within the eutectic region. The transformation is mostly complete after 12 h, but after 24 h of homogenization it is fully complete as all samples, except the 24 h homogenized one, contain both the metastable Al6 Fe and the stable Al13 Fe4 phase.