Experimental investigation and thermodynamic calculation of the Al–Fe–P system at low phosphorus contents

Al–Fe–P alloys ingots were cast and annealed at 450 °C, and then analyzed with scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM–EDS) and X-ray diffraction (XRD) to determine phase equilibria in the Al–Fe–P system when the P content was below 20 at%. No ternary compound was found in the system. Moreover, P cannot dissolve in the Al–Fe compounds, e.g. Fe2Al5, Fe4Al13 and FeAl2. While the maximum solubilities of P in BCC_B2(FeAl), Al in Fe3P and Fe2P are 2.7 at%, 2.1 at% and 1.7 at%, respectively, and 1.8 at% Fe was detected in AlP. Furthermore, a thermodynamic description of the Al–Fe–P system was carried out on the basis of the present experimental results. The thermodynamic parameters of the boundary binary systems were directly cited from literatures. All the binary intermetallics phases were assumed to have no ternary solubility. Reasonable agreement of the phase equilibria in the Al–Fe–P ternary system between thermodynamic extrapolation and experiments was achieved.