Thermodynamics of the deoxidation equilibrium of aluminum in liquid nickel and nickel-iron alloys

The deoxidation equilibrium of aluminum in liquid nickel equilibrated with solid alumina has been measured at the temperature ranges from 1 823 to 1 973 K using the sampling technique in order to investigate the equilibrium between aluminum and oxygen in liquid nickel for the refractory alloy or superalloy. For the deoxidation reaction in pure liquid nickel, i.e.: Al2O3(s)=2<(Al)under bar>+3 (O) under bar the temperature dependence of the equilibrium constants, K-Al(=a(Al)(2) . a(O)(3)/aAl(2)O(3)), was expressed to be: log K-Al=-28 770/T+1.67 1 823-1 973 K while the deoxidation product, K-Al' (=[%Al](2)[%O](3))) and the effect of aluminum on the activity coefficient of oxygen in liquid nickel were obtained to be: log K-Al'=log K-Al+1.47 (3[%Al]+3.4[%O]) log f(O)(Al)=-1.47[%Al] Al<1.1 mass%, 1823-1973 K The deoxidation equilibrium of aluminum in liquid nickel-iron binary alloys with 0.01-0.1 mass% aluminum has been measured up to 50mass% 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 f(O)(Fe)+2/3 log f(Al)(Fe)=-0.028[%Fe], up to around 10 mass% iron at 1 923 K. The effect of nickel on the activity coefficient of aluminum in liquid iron-nickel based on liquid iron were also discussed using log K-Al(Fe) in liquid iron and the present results.