Experimental investigation and thermodynamic modeling of the ternary Al–Cu–Fe system

The constitution of the ternary system Al–Cu–Fe in the region above 40 at.% Al at 600 °C is investigated by means of x-ray diffraction, metallography, scanning electron microanalysis, energy dispersive x-ray spectroscopy, and differential thermal analysis. The phase equilibria in the Al-rich corner are clarified by the valuable experimental evidence for the four-phase reaction L + λFe₄Al₁₃↔ (Al) + ω at 600.7 °C and experimental findings that the phase αFe₄CuAl₂₃was not detected. A thermodynamic model of the Al–Cu–Fe system was then performed over the entire composition range by taking into account the phase diagram data above 560 °C from the literature and the present work. This work challenged the modeling of the considerably complex order–disorder phase transition between bcc_A2 and bcc_B2 phases and the miscibility gap of bcc_B2 phase using the modified sublattice model.