Deoxidation Equilibrium of Hafnium in Liquid Iron, Nickel and Iron-Nickel Alloys.

Abstract

The deoxidation equilibrium of hafnium in liquid iron, nickel and iron-nickel binary alloys has been studied at the temperature ranges from 1873 to 1973 K using hafnia crucibles. The effect of temperature on the equlibrium constant of the deoxidation reaction in liquid iron with hafnium was found to be: log KHf(Fe)(=aHf·aO2)=-35840/T+11.39 while the deoxidation product in iron was expressed as follows: logK'Hf(Fe) (=[%Hf] [%O]2)=logKHf (Fe)+5.85(2[%Hf]+11.1 [%O]) (0.01-0.1 mass% Hf) The temperature dependence of the equilibrium constant of the deoxidation in liquid nickel was determined as the expression. log KHf(Ni)=aHf·aO2= –33800/T+8.40 in the meantime, the deoxidation product in nickel was given by: log K'Hf (Ni) (=[%Hf] [%O]2)=log KHf (Ni)+9.75 (2 [%Hf]+11.1 [%O]) (0.002-0.1 mass% Hf) The deoxidation of iron-nickel binary with hafnium was measured over whole concentration ranges of the binary system at temperatures of 1873 and 1923 K. The activity coefficients of oxygen and hafnium in the binary based on pure liquid iron were given by the following expression: log fO(Fe)Ni+ 1/2 log fHf(Fe)Ni=0.005 [%Ni] below 60 mass% of nickel, while the activity coefficients on the nickel basis were expressed by: log fO(Ni)Fe+ 1/2 log fHf(Ni)Fe= –0.025 [%Fe] below 10 mass% of iron.