Thermodynamics of titanium and nitrogen in an Fe-Ni melt

Abstract

The equilibrium solubility of titanium and nitrogen in Fe-Ni melts was measured in the presence of pure solid TiN under various nitrogen pressures in the temperature range of 1843 to 1923 K. The activity coefficients of titanium and nitrogen relative to a 1 mass pct standard state in liquid iron were calculated from the experimental results for Fe-Ni alloys of nickel contents up to 30 mass pct. Nickel decreases the activity coefficient of titanium, but it increases the activity coefficient of nitrogen in an Fe-Ni-Ti-N melt. Therefore, the effect of nickel on the solubility product of TiN is not significant. The first- and second-order interaction parameters of nickel on titanium (e(Ti)(Ni) and r(Ti)(Ni), respectively) were determined to be -0.0115 and 0 at 1873 K, respectively. Similarly, the interaction parameters of nickel on nitrogen (e(N)(Ni) and r(N)(Ni), respectively) were determined to be 0.012 and 0, respectively, at 1873 K. The temperature dependence of these interaction parameters was also determined.