Equilibrium between Hafnium and Oxygen in Liquid Iron and Nickel

Abstract

The deoxidation equilibrium of hafnium in liquid iron and nickel has been measured at the temperature range from 1600°C to 1750°C using hafnia crucibles with a view to understanding the equilibrium between hafnium and oxygen in iron and nickel.
The results obtained are summarized as follows:
Liquid iron, log K_Hf(Fe) ( = a_Hf·a²_O) = - 35840/T + 11.39
log K'_Hf(Fe) ( = [ %Hf] [ % O]²) = log K_Hf(Fe) + 5.85 (2[%Hf] + 11.1[%O]) (0.010.1 mass% Hf)
Liquid nickel, log K_Hf(Ni) (= a_Hf·a²_O = - 33800/T + 8.40
log K'_Hf(Ni) (= [%Hf][%O]²) = log K_Hf(Ni)) + 9.75(2[%Hf]+ 11.1[%O]) (0.0020.1mass% Hf)
The activity coefficients of oxygen and hafnium in nickel-iron alloys based on pure liquid nickel are expressed by the following equation:
logƒ^Fe_O(Ni) + 1/2 logƒ^Fe_Hf(Ni) = -0.025[ %Fe]
up to 10 mass pct of iron at temperatures between 1600°C and 1650°C.