Thermodynamic Assessment of the Fe-B System in the Ssol5 and User Databases

Abstract

Thermodynamic assessment of Fe-B system, including phase diagram, Gibbs energy, enthalpy, heat capacity and activity, was performed in the ThermoCalc software ver. 4.1 (Sweden). Two databases were used: the commercial SSOL5 database for solid solutions (substitutional approach) and the USER made database based on work of T. Van Ro mpaey et al. (intersticial approach). Results obtained were c ompared with experimental data gathered from work of M. Van Ende et al. In low boron regime the curve of the Fe -B phase diagram is represented more reliable in the USER database. However, temperatures of the phase transformations are calculated with more accuracy in the SSOL5 database. For boron content higher than 0.3 mole fraction phase transformation temperatures are better assessed in the USER database, except for melting point of the Fe 2 B phase. Gibbs energy, enthalpy and heat capacity of the FeB and t he Fe 2 B are difficult to evaluate because experimental data are spread and inaccurate. Activities of iron and boron in liquid Fe -B alloy, calculated at selected temperatures, are almost identical for both databases. paramount importance.