Thermodynamics of iron-aluminum alloys at 1573 K

The activities of iron (Fe) and aluminum (Al) were measured in Fe-Al alloys at 1573 K using the ion-current-ratio technique in a high-temperature Knudsen cell mass spectrometer. The Fe-Al solutions exhibited negative deviations from ideality over the entire composition range. The activity coefficientsγ Fe, andγ A1 are given by the following equations as a function of mole fraction (x Fe,x Al):

0<χA1<0.4
ln(γ(Fe))=−4.511(±0.008)χ^(2)(A1)
ln(γ(A1))=−4.462(±0.029)χ^(2)(Fe) +0.325(±0.013)
0.6<χ(A1)<1.0
ln(γ(Fe))=−4.065(±0.006)χ^(2)(A1)+0.099(±0.003)
ln(γ(A1))=−4.092(±0.026)χ^(2)(Fe)+0.002(±0.001)

The results showed good agreement with those obtained from previous investigations at other temperatures by extrapolation of the activity data to 1573 K.