Thermodynamics of aluminum, nitrogen and AIN formation in liquid iron

Abstract

Thermodynamics of aluminum, nitrogen and AIN formation In liquid iron was investigated using the metal-nitrlde-gas equilibration under various nitrogen partial pressures In the temperature range of 1 873-1 973 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 AIN In liquid iron as follows. θNAl = -332.2/7+0.194 θAlAl = 111.0/7-0.016 AlN(s)=Al+N log/C AlN = -16 560/7+7.4 Thermodynamics of aluminum In liquid iron could be well described by Darken's quadratic formalism, and the values of αFe-Al and γAlo, were determined as follows. αFe-Al=-1 112/T-0.585 γAlo = - 185.0/7+0.165 © 2007 ISIJ.