Solubility of Nitrogen in Liquid Chromium and Chromium-Iron Alloys

Abstract

The solubility of nitrogen in liquid chromium and chromium-iron alloys has been studied by a sampling method at the temperatures of 1550-1780°C and under 0.04-1.0atm of nitrogen.
The equilibrium constant of the solution reaction and the activity of nitrogen in liquid chromium and chromium-iron alloys were determined by applying the interstitial model to the experimental results.
The results obtained are summarized as follows:
(1) Nitrogen dissolved in liquid chromium and chromium-iron alloys up to 50% Fe does not obey the Sieverts' law, and the solubility of nitrogen in liquid chromium is given by the following equation.
log K(Z)=5515/T-3.19₃,
K(Z)=a_N/√<P_N2>=ψ_NZ_N√<P_N2>
(2) The activity coefficients of nitrogen based on pure liquid chromium are expressed as follows:
log ψ^N_N(Cr)=(4235/T-1.51₃)•Y_N Y_N<0.21
log ψ^Fe_N(Cr)=1.80•Y_Fe Y_Fe<0.7
(3) The activity coefficients of nitrogen in liquid iron-chromium alloys based on pure liquid iron are shown by the following equations:
log γ^Cr_N(Fe)=(-13765/T+3.10)•X_Cr X_Cr<0.16
log f^Cr_N(Fe)=(-148/T×0.033)•[%Cr] [%Cr]<15
where, Y_N Z_N: the mole ratio and the lattice ratio of nitrogen in the liquid metal, respectively.