Thermodynamics of Aluminum, Nitrogen and AlN formation in Liquid Iron

Abstract

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 AlN 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.
e_N^Al=−332.2/T+0.194
e_Al^Al=111.0/T−0.016
AlN (s)=Al+N
log K_AlN=−16 560/T+7.4
Thermodynamics of aluminum in liquid iron could be well described by Darken's quadratic formalism, and the values of α_Fe–Al and γ°_Al were determined as follows.
α_Fe–Al=−1 112/T−0.585
γ_Al°=−185.0/T+0.165