Activity of Phosphorus in Liquid Fe-P and Fe-P-C Alloys

Abstract

The activity of phosphorus in liquid iron and iron-carbon alloys has been measured by distribution experiments between the immiscible liquid iron and silver at temperatures of 1300°-1600°C and in the composition range up to 21.0 weight percent phosphorus. The results obtained were treated by the model of interstitial solution proposed by J. CHIPMAN. It has been found that the apparent distribution constant of phosphorus is expressed with a linear function which has a inflection at the composition of Fe₃P at constant temperature.
The results obtained are summarized as follows:
The distribution constant of phosphorus:
logK (=a^Ag_p/a^Fe_p) =-7180 /T+0.54
The activity coefficient:
logψ^p_p=0.982y_p…0y_p<0.33
logψ^p_p=-2.32+7.96y_p…0.33y_p<0.5
logψ^c_p=1.18y_c…y_p<0.33, y_c<0.17
The interaction parameter:
ε^p_p= (∂ln_γp/∂X_p) X_Fe→1=4.26±0.5
ε^c_p= (∂ln_γp/∂X_c) X_Fe→1=4.72±1.1