Isotope Exchange Measurements of the Interfacial Reaction Rate Constant of Nitrogen on Fe-Mn alloys and an Advanced High-Strength Steel

Precise control of dissolved nitrogen is required for producing Third-Generation Advanced High-Strength Steels (AHSS). Compared with well-documented thermodynamic data, the data on the kinetics of nitrogen dissolution in these steels are limited. The isotope exchange technique (¹⁵N–¹⁴N exchange reaction) was applied to measure the nitrogen reaction rate at different temperatures, on pure liquid iron, liquid iron containing different levels of manganese, and liquid Fe-Mn-Al-Si steel with a Third-Generation AHSS composition. The increase in the interfacial reaction rate with increased temperature corresponded to an activation energy of 144.2 kJ/mol for pure iron. For Fe-Mn alloy, the interfacial reaction rate increased with the increased temperature and increased manganese content. For liquid AHSS (Fe-Mn-Al-Si), the interfacial reaction rate was approximately one third of the rate for pure liquid iron, at the same temperature, with a corresponding activation energy of 160.5 kJ/mol.