Thermodynamic behavior of nitrogen in Fe-Cr-Ti-Al-Si-N alloy melts was investigated by measuring the nitrogen solubility and solubility product of TiN and AlN by the metal/gas and metal/nitride/gas equilibration techniques at 1 823-1 873 K, respectively. The nitrogen solubility data measured in Fe-Cr-Ti, Fe-Cr-Si, Fe-Ti-Al and Fe-Cr-Al alloy melts was thermodynamically analyzed to determine the second-order cross-product parameters of Cr-Ti, Cr-Si, Al-Ti and Cr-Al on nitrogen in liquid iron using Wagner's formalism. By considering the cross-product effect on nitrogen determined in the present study, the effects of the alloying elements on the solubility product of TiN and AlN in the multicomponent Fe-Cr-Ti, Fe-Ti-Al and Fe-Cr-Al alloy melts were successfully reproduced over the wide temperature range.

The effect of silicon on TiN formation in liquid iron was studied by measuring the nitrogen solubility and TiN solubility product in liquid Fe-Ti alloys with silicon additions under various nitrogen partial pressures in the temperature range of 1 823-1 923 K. The first-and second order interaction parameters of silicon on titanium, e Ti Si and r Ti Si were determined as − 0.038 and 0, respectively, and the second-order crossproduct parameter of titanium and silicon on nitrogen in liquid iron, r N Ti,Si was determined as 0. Temperature dependence of these parameters were negligible.