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 degrees C is investigated by means of x-ray diffraction, metallography, scanning electron microanalysis with 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 + lambda Fe4Al13 <-> (Al) + omega at 600.7 degrees C and by the experimental findings that the phase alpha Fe4CuAl23 was not detected. A thermodynamic modeling of the Al-Cu-Fe system was then performed over the entire composition range by taking into account the phase diagram data above 560 degrees 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.