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

Abstract

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.