Experimental study and thermodynamic assessment of the Al-Fe rich side of the Al-Zn-Fe system at 300 and 550 °C

The phase relations of the Al-Zn-Fe system on the Al-Fe rich side at 300 and 550 degrees C were studied by means of the diffusion couple technique. The morphologies of Al96.2Zn3.8/Fe diffusion couples were observed by scanning electron microscopy (SEM) and the composition profiles were determined using energy dispersive spectroscopy (EDS). The intermetallics layer formed between the Al96.2Zn3.8 and Fe end-members were mainly Fe2Al5 phase. The diffusion path identified at 300 degrees C was (Al) -> Fe4Al13 -> Fe2Al5 -> bcc(Fe) -> (Fe), and that was (Al) -> Fe4Al13 -> Fe2Al5 -> (Fe) at 550 degrees C. Based on the literature information and the current experimental results, the Al-Zn-Fe system was re-assessed thermodynamically with a CALPHAD approach. The calculated phase diagrams at 300, 450 and 550 degrees C agreed well with current experimental results as well as the data from the literature. (C) 2012 Elsevier Ltd. All rights reserved.