Thermodynamics of Nitrogen Solubility and AlN Formation in Multi-Component High Mn Steel Melts

Thermodynamics of nitrogen and AIN formation in multi-component liquid iron alloys containing Mn, Al, Si and C was investigated by the metal/gas and the metal/nitride/gas equilibration techniques under reduced nitrogen partial pressures in Ar-N-2 gas mixture. The N solubility was measured in binary Fe-Mn and Fe-Si alloy melts, and ternary Fe-Mn-Si, Fe-AI-Si, Fe-Mn-C and Fe-Si-C alloy melts over wide com position range at 1 773-1 873 K. Using Wagner's formalism, the effect of alloying elements on the N solubility was described as the first- and second-order interaction parameters as well as the second-order cross-product parameters. The validity of the interaction parameters determined in the present study was checked by measuring the N solubility and AIN solubility product for a typical TWIP steel composition melt of Fe-25% Mn-0.3% Si-0.6% C-Al at 1 723-1 873 K.