1998 Volume 38 Issue 12 Pages 1287-1291
The activity of chromium in molten Fe–Cr–C alloy was measured at 1823 K using chemical equilibration technique in the dilute Cr concentration region. It was found that chromium in Fe–Cr–C alloy showed Henrian behavior up to 3 mass% Cr and that the activity coefficient of chromium at infinitely dilute solution in Fe–Cr alloy was 3.90 at 1823 K.
The effects of carbon on the activity coefficient of chromium at infinitely dilute solution in Fe–Cr–C alloy could be expressed as follows;
ln γCr(S)o=1.29–7.09XC at 1823 K
There is little temperature dependence of the activity of chromium at carbon saturated condition.
The standard Gibbs energy of mixing for Fe–Cr alloy and Fe–Cr–Csatd alloy was calculated using the Gibbs–Duhem relationship. The results indicated that the affinity between chromium is larger than that of chromium for iron in Fe–Cr alloy. But the affinity between chromium and carbon is increased with increasing carbon.