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 °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 °C was (Al)→Fe4Al13→Fe2Al5→bcc(Fe)→(Fe), and that was (Al)→Fe4Al13→Fe2Al5→(Fe) at 550 °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 °C agreed well with current experimental results as well as the data from the literature.