Deoxidation Equilibrium of Titanium in the Iron–Nickel Melts

The oxygen solutions in the titanium-containing Fe–Ni melts have been thermodynamically analyzed. When the nickel content rises to 40%, the deoxidation ability of titanium decreases but then it sharply rises with increasing nickel concentration in melt. This can be explained by the fact that although the bond strength of titanium in nickel is considerably stronger in comparison with iron (γ°Ti(s)(Fe)=0.0083; γ°Ti(s)(Ni)=0.00019), but the bond strength of oxygen in nickel is appreciably weaker that in iron (γ°O(Fe)=0.0105; γ°O(Ni)=0.357). The oxygen solubility curves pass through a minimum whose position shifts to the higher titanium concentrations with an increase in the nickel content from 0.564% Ti for pure iron to 0.633% Ti for pure nickel. The further addition of titanium causes an increase in the oxygen content in melt. Equilibrium points of oxide phases TiO2, Ti3O5 and Ti2O3 for different alloy compositions at 1873 K were determined. The published results devoted to the oxide phases in iron and nickel deoxidized with titanium are summarized. Deoxidation of Fe–40%Ni melts with titanium was experimentally studied. The experimental and calculated results are in good agreement. The deoxidation abilities of titanium, chromium, manganese, vanadium, silicon, carbon, and aluminum in different Fe–Ni alloys are compared.