Thermodynamics of aluminum, nitrogen and AIN formation in liquid iron

Thermodynamics of aluminum, nitrogen and AlN formation in liquid iron was investigated using the metal-nitride-gas equilibration under various nitrogen partial pressures in the temperature range of 1873-1973 K. The nitrogen solubility in liquid iron decreased with aluminum additions. Pure solid AIN was formed at critical contents of aluminum and nitrogen in liquid iron. The experimental results were thermodynamically analyzed using Wagner's interaction parameter formalism to determine the first-order interaction parameter of aluminum and nitrogen, the first-order self interaction parameter of aluminum, and the equilibrium constant for the formation of pure solid AlN in liquid iron as follows. eNAl = -332.2/T+ 0.194, eAlAl = 111.0/T - 0.016, AlN (s)=Al+ N, log KAlN= -16560/T+7.4. Thermodynamics of aluminum in liquid iron could be well described by Darken's quadratic formalism, and the values of alphaFe-Al and etaAl deg were determined as follows. alphaFe-Al= 1112/T-0.585, gammaAl deg =-185.0/T+0.165.