Thermodynamics of the Deoxidation Equilibrium of Aluminum in Liquid Nickel and Nickel-Iron Alloys.

Abstract

The deoxidation equilibrium of aluminum in liquid nickel equilibrated with solid alumina has been measured at the temperature ranges from 1823 to 1973 K using the sampling technique in order to investigate the equilibrium between aluminum and oxgen in liquid nickel for the refractory alloy or superalloy. For the deoxidation reaction in pure liquid nickel. i.e.:Al2O3(s) =2Al+3O the temperature dependence of the equilibrium constants, KAl (=aAl2·aO3/aAl2O3), was expressed to be:log KAl=–28770/T+1.67 1823–1973 Kwhile the deoxidation product, K'Al (=[%Al]2[%O]3), and the affect of aluminum on the activity coefficient of oxgen in liquid nickel were obtained to be:log K'Al=log KAl+1.47 (3[%Al]+3.4[%O])log fOAl=–1.47 [%Al]Al<1.1 mass%, 1823–1973 KThe deoxidation equilibrium of aluminum in liquid nickel–iron binary alloys with 0.01–0.1 mass% aluminum has been measured up to 50 mass% iron. The effect of iron on the activity coefficients of oxygen and aluminum in liquid nickel–iron alloys based on pure liquid nickel were estimated as the following expression:log fOFe+2/3log fAlFe=–0.028 [%Fe]up to around 10 mass% iron at 1923 K.The effect of nickel on the activity coefficient of aluminum in liquid iron-nickel based on liquid iron were also discussed using log KAl(Fe) in liquid iron and the present results.