The AlN solubility product in liquid iron containing manganese up to 22 mass% were measured by the metal-nitride-gas equilibration technique in the temperature range from 1 823 to 1 873 K. Manganese significantly increased the AlN solubility product in liquid iron primarily due to the large effect of manganese on the nitrogen solubility. Using the Wagner's formalism, the experimental results were thermodynamically analyzed to determine the thermodynamic interaction parameters between manganese and aluminum in high Mn-Al alloyed liquid steels as follows;(Mn ≤ 22 mass%, Al ≤ 1.8 mass%, 1 823-1 873 K) KEY WORDS: high manganese steel; AlN; aluminum; nitrogen; interaction parameter.

The nitrogen solubility in liquid Fe-C alloys containing carbon up to 5.2 mass% has been measured under reduced nitrogen partial pressures in the temperature range of 1 773-1 873 K. Previous studies on the C-N interaction in liquid iron have shown marked disagreement on its temperature dependency and the order of interaction. By the gas-liquid metal equilibration technique using a high frequency induction furnace with an accurate temperature measurement, precise nitrogen solubility data were obtained. The interaction between carbon and nitrogen in liquid iron has been expressed in terms of the first-and second-order interaction parameters. No temperature dependence of these values was observed in the temperature range from 1 773 to 1 873 K.(1.14 ≤ mass% C ≤ 4.95 at 1 773 K, 0 ≤ mass% C ≤ 5.2 at 1 823-1 873 K) KEY WORDS: nitrogen solubility; Fe-C alloy; carbon; interaction parameter.

Thermodynamic behavior of nitrogen in the entire range of the Fe-Mn-Al-Si-C liquid solution was modeled based on the critical evaluation and optimization of all available experimental data. The Gibbs energy of liquid solution was described using the Modified Quasichemical Model (MQM) in the pair approximation, instead of classical Wagner Interaction Parameter Formalism, to consider the strong interactions between species in liquid state. In particular, the dissolution behavior of N and formation of AlN in the entire ternary and higher order liquids were accurately predicted from the MQM only with binary model parameters of N.

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